Implement bun unlink {packageName}

[brainkim]

What does this PR do?

Saw that bun unlink {packageName} was unimplemented and gave it a shot. Fixes #7852.

• Documentation or TypeScript types (it's okay to leave the rest blank in this case)
• Code changes

How did you verify your code works?

• I checked the lifetime of memory allocated to verify it's (1) freed and (2) only freed when it should be
• I included a test for the new code, or an existing test covers it
• JSValue used outside of the stack is either wrapped in a JSC.Strong or is JSValueProtect'ed
• I wrote TypeScript/JavaScript tests and they pass locally (bun-debug test test-file-name.test)

It seemed like manager.updatePackageJSONAndInstallWithManager() in install.zig mostly handles the case of unlinking. I accounted for three cases when writing this code:

• A new package is linked and unlinked
• An existing unlinked package is linked and unlinked
• A package linked with --save is unlinked with --save

The current summary is not that helpful, but I haven’t yet wrapped my head around how the lockfile diffing works. The tricky thing with unlink is that it typically won’t create package.json changes, so I’m unsure how to show the unlinked packages as removed.

[brainkim]

The previous minimal bun remove logic triggers on do.write_package_json, but bun unlink defaults to --no-save and I think running removal/unlinking logic on do.install_packages makes more sense.

[brainkim]

I could maybe work on the summary output, but the current seems fine for now?