remove quadratic limitation on counting quotes

[aryairani]

The old implementation called Text.breakOnAll repeatedly, which could be slow, so it was capped at 10 quotes. The new implementation instead just calls Text.group once instead.

The PR could use a before and after check with a string with more than 10 consecutive " in it, and we should see that the rendering is improved with the PR. Existing tests show """ correctly being escaped as """" though, and since the PR removes the reference to 10, there isn't actually anything special about 10 going forward.

[aryairani]

Things I debated:

I considered writing a single function to fuse all of the operations from longestRun into a single loop, but in the end I went with the Copilot-written one-liner.