Detect .cts and .mts files in loader utils

[htunnicliff]

What's the problem this PR addresses?

Fixes #6595.

This change lets Yarn's ESM loader correctly detect TypeScript files that use .mts or .cts extensions.

How did you fix it?

I updated getFileFormat() in loaderUtils.ts to treat .mts as having a "module" format and .cts as having a "commonjs" format.

Checklist

• I have read the Contributing Guide.

• I have set the packages that need to be released for my changes to be effective.

• I will check that all automated PR checks pass before the PR gets reviewed.

[clemyan]

You need to run yarn update:pnp:hook to compile and use the hook.

This change enables loading .cts and .mts files, but disables type-stripping entirely for them. You need the commonjs-typescript and module-typescript formats for that.

Please note that not all Node versions we support has type-stripping (and the aforementioned formats), and I don't fully understand how those formats interact with the --experimental-type-stripping and --no-experimental-type-stripping flags across Node versions. You need to factor those into determining what format to use here to match Node's default behavior, and add tests to test for those behavior.

[clemyan]

plugin-pnp and cli also need releases