Do not merge file patterns into a single regular expression

[MichaelMitchell-at]

Fixes #61103

Recommend viewing using Github's "Unified" view as some of these lines are quite long.

Benchmark

Running tsc on this repo which demonstrates slow performance: https://github.com/MichaelMitchell-at/typescript_slow_wildcards_repro

Before:

$ hyperfine 'node ./built/local/tsc.js -p ../typescript_slow_wildcards_repro/tsconfig.json'
Benchmark 1: node ./built/local/tsc.js -p ../typescript_slow_wildcards_repro/tsconfig.json
  Time (mean ± σ):      7.720 s ±  0.237 s    [User: 7.780 s, System: 0.071 s]
  Range (min … max):    7.480 s …  8.280 s    10 runs

After:

$ hyperfine 'node ./built/local/tsc.js -p ../typescript_slow_wildcards_repro/tsconfig.json'
Benchmark 1: node ./built/local/tsc.js -p ../typescript_slow_wildcards_repro/tsconfig.json
  Time (mean ± σ):     365.1 ms ±  14.9 ms    [User: 680.9 ms, System: 45.8 ms]
  Range (min … max):   353.1 ms … 403.9 ms    10 runs

[MichaelMitchell-at]

Hm, after testing this change on our codebase, which is on the order of thousands of projects, I'm seeing a net performance decrease, but each individual project is sometimes faster or slower with this change. It seems that there's more nuance to this.

[typescript-bot]

With 6.0 out as the final release vehicle for this codebase, we're closing all PRs that don't fit the merge criteria for post-6.0 patches. If you think this was a mistake and this PR fits the post-6.0 patch criteria, please post to the 6.0 iteration issue with details (specifically, which PR and which patch criteria it satisfies).

Next steps for PRs:

• For crash bugfixes or language service improvements, PRs are currently accepted at the typescript-go repo
• Changes to type system behavior should wait until after 7.0, at which point mainline TypeScript development will resume in this repository with the Go codebase
• Library file updates (lib.d.ts etc) continue to live in this repo or the DOM Generator repo as appropriate