fix: Fix Chrome stack overflow during highlighting

[varungandhi-src]

Using the spread operator with large arrays can trigger a
stack overflow in Chrome/V8. For example, see:

• "inconvenient" stack overflow when using spread operator - changing stack size does not work nodejs/node#16870

In a highlighting context, we can have 10k-100k occurrences
in a file, so let's avoid using the spread operator.

Fixes https://linear.app/sourcegraph/issue/GRAPH-772

Test plan

Manually tested against sample file.

Changelog

• Fixes a Chrome-specific stack overflow when highlighting large files.

[eseliger]

Wonder what a flamegraph of this looks like, and if some sort of chunking (like push 1k at a time) could help in case it's bad - but approving for the fix.

[varungandhi-src]

Wonder what a flamegraph of this looks like, and if some sort of chunking (like push 1k at a time) could help in case it's bad

This operation should only be happening once per blob, so I don't think it's worth micro-optimizing the pushes; the lookups are much more expensive.

[camdencheek]

Good find -- thank you for the fix!