[PWGLF] Update on Xi1820: Check DCA to V0, Prevent V0 daughter mixing

[mjkim525]

This PR includes the following updates:

1. Added QA plots for the DCA to V0 in the K0s–Lambda channel to support cut studies for the invariant-mass distribution construction.

2. For the same reason, added a check on the track IDs of the V0 daughters to prevent mixing between daughters from the same V0 candidate.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 4 warnings, 🔕 5 disabled

[alibuild]

Error while checking build/O2Physics/code-check for 21120dc at 2026-07-07 15:31:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 3 errors and 137 warnings.'
Found 3 errors and 137 warnings.
++ [[ 3 -gt 0 ]]
++ cat /sw/BUILD/4dcf5df96f4ac7b3c2b2ac4c0eab30231f395413/O2Physics-code-check/errors.txt
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:417:20: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:633:9: error: do not use 'else' after 'return' [readability-else-after-return,-warnings-as-errors]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:678:9: error: do not use 'else' after 'return' [readability-else-after-return,-warnings-as-errors]
++ [[ 137 -gt 0 ]]
++ cat /sw/BUILD/4dcf5df96f4ac7b3c2b2ac4c0eab30231f395413/O2Physics-code-check/warnings.txt
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:439:43: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:441:29: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:445:36: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:447:40: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:451:57: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:453:57: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:458:56: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:468:47: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:473:63: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:476:82: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:478:82: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:482:67: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:484:82: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:486:82: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:492:80: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:496:66: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:498:66: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:501:71: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:511:43: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:513:29: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:517:37: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:519:41: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:523:58: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:525:58: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:530:58: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:534:67: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:544:48: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:548:64: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:553:78: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:555:82: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:559:77: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:561:77: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:565:63: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:567:63: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:570:71: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:602:23: warning: statement should be inside braces [readability-braces-around-statements]
PWGLF/Tasks/Resonances/xi1820Analysis.cxx:617:51: warning: statement should be inside braces [readability-braces-around-statements]
[0 more errors; see full log]

Full log here.