Stubbed out all builtin functions/tests

[arduano]

Added stubs for all builtins and their respective test modules, ordered in the order they appear in the Nix manual
https://nixos.org/manual/nix/stable/language/builtins.html

[urbas]

Mind adding a couple of tests for this function? Feel free to do in a separate PR.

[arduano]

@urbas Can you please approve again, or enable approvals to stay after commits

[arduano]

Also FYI

For the next PR I'm planning to try using graphite https://graphite.dev/
There will be multiple PRs referencing each other, they all depend on each other but it makes it easier for me to divide logical changes from 1 massive PR to like 5+ smaller PRs for you to review independently

I've used graphite before, but would be interesting to try it on a smaller project like this

[urbas]

Nix seems to return "baz" for this test:

% nix eval --expr 'builtins.baseNameOf "/foo/bar/baz/"'
"baz"

Suggested change

	Value::Str("".into())
	Value::Str("baz".into())

Btw, the basename CLI tool also returns baz in this case.

[urbas]

Also FYI

For the next PR I'm planning to try using graphite https://graphite.dev/ There will be multiple PRs referencing each other, they all depend on each other but it makes it easier for me to divide logical changes from 1 massive PR to like 5+ smaller PRs for you to review independently

I've used graphite before, but would be interesting to try it on a smaller project like this

I haven't used graphite before, will give it a go.

Btw, apologies for the slow responses. Was traveling a lot these days.