Add support for multi-file CLI command scripts embedded into the lute executable

[vrn-sn]

Summary

In this PR, we add support for running command-line Luau scripts that are stored in the cli/commands directory.

If we have cli/commands/foo.luau or cli/commands/foo/init.luau, running lute foo will automatically execute the contents of that script (with support for relative requires as well).

Implementation details

We create a new CliVfs that can optionally be embedded in RequireVfs. The CLI enables this, but vm.create does not, as it does not need a custom VFS for command-line scripts. The actual implementation of the VFS is nearly identical to StdLibVfs.

The embedding of the CLI scripts is done using Luthier to generate source files for a new Lute.CLI.Commands target. This is similar to how the @std libraries were embedded into the Lute.Std target.

• Move Lute to Luau's new Luau.Require library #138
• Generate SHA-256 hash for std/libs libraries to track stale generated files #205

While working on this, I noticed that luthier.luau was incomplete. Due to the lack of an os.walk API like we have in Python, luthier.luau doesn't correctly handle nested directories that need to be embedded. To solve this, I have added a traverseFileTree function that effectively accomplishes the same thing.

Because of slight differences in the order files are processed by os.walk and traverseFileTree, luthier.py and luthier.luau spit out different hashes. I think this is fine. When only using one of the tools in isolation, the caching seems to work as expected.