feat(unstable): add Deno.getUid

[kt3k]

closes #13493

[bartlomieju]

@kt3k looks good, I have two nitpicks:
a) maybe use Deno.getUid()?
b) should we add Deno.getGid() too?

[kt3k]

@bartlomieju

a) maybe use Deno.getUid()?

I'm not strongly against that. I chose this name because we tend to use linux syscall names as is. ex. chmod, chdir, lstat, utime, futime, flock, funlock, etc

If we try to make it more descriptive, I guess Deno.getUserId might be another option. (similar to Deno.makeTempDir instead of Deno.mktemp)

I'd like to hear more opinions from other members

b) should we add Deno.getGid() too?

I think we should. That's also useful for more precise implementation of fs.access

[bartlomieju]

@kt3k sounds good!

[jorroll]

FWIW, I initially interpreted Deno.getUid() as "get unique ID". Though hopefully, when hovering over the method in VSCode, I would have noticed the JSDoc comment if I ran across this in an application. Its usage context might also have cleared up any confusion.