Implement an `lcov` coverage reporter for `bun test`

[Jarred-Sumner]

Format

The only thing we are missing for lcov to work well is function names. JSC doesn't include them.

Otherwise, I think we can just write the file

[hrgdavor]

I switched a small project to bun test because jsx just works, and I do not think nodejs will allow that in their native test runner anytime soon (or if added would be slow likely).

current output in console is usable, but lcov will be great, for integrating and generating pretty html reports.

[jbergstroem]

current output in console is usable, but lcov will be great, for integrating and generating pretty html reports.

..and uploading reports to tools such as codecov and coveralls.