fix: cache output number parsing in createStringInterpolator

[literalpie]

Why

Starting in version 10.1.0, this code is very slow when showing a chart with a large number of points.

What

Instead of calculating the value in every iteration of the loop, the numbers are only calculated once.

Checklist

• Ready to be merged

[changeset-bot]

🦋 Changeset detected

Latest commit: 4313236

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 9 packages

Name	Type
@react-spring/shared	Patch
@react-spring/animated	Patch
@react-spring/core	Patch
@react-spring/mock-raf	Patch
@react-spring/parallax	Patch
@react-spring/rafz	Patch
@react-spring/types	Patch
@react-spring/three	Patch
@react-spring/web	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

[literalpie]

heads up: the contributing.md file implies that only maintainers need to worry about changesets, and says

With react-spring we bump every package to the same version, so flag them all

I'm guessing "maintainers only" isn't right based on the above comment, and I'm not sure if "flag them all" is right, since I see other PRs that don't flag all packages

[joshuaellis]

Thanks for the contribution, i've done a follow up PR for the contributing recommendations – #2549, thanks for flagging.