feat: lockfile support

[mrcjkb]

Closes #34.

The documentation says luarocks will use a lockfile if there is one in the cwd.
But I haven't confirmed this yet.

This needs some vigorous testing.

How it works

Adding/updating/removing rocks:

• We add a --pin flag to the install command
• luarocks creates a luarocks.lock file in the rock's install tree (for all transitive dependencies of the installed rock)
• We add the path to the rtp
• We load the lockfile and use it to update our rocks-lock.toml

Syncing rocks:

• We get the locked dependencies from our rocks-lock.toml
• We use those to create a luarocks.lock in a temp directory
• We set the cwd to the location of the lock file for any install commands

[github-actions]

Review Checklist

Does this PR follow the Contribution Guidelines? Following is a partial checklist:

Proper conventional commit scoping:

• For example, fix(installer): some installer bugfix

• Pull request title has the appropriate conventional commit prefix.

If applicable:

• Tested
  • Tests have been added.
  • Tested manually (steps in PR description).
• Updated documentation.

[mrcjkb]

🤔 maybe we should just call the file rocks.lock instead of rocks-lock.toml.

[mrcjkb]

I just can't get the test cases to succeed (╯°□°)╯︵ ┻━┻

It looks like it could be something to do with the neovim scheduler? Not sure how to get busted working with that.

[mrcjkb]

This PR is pretty much ready. But I would like to merge #245 first.

[mrcjkb]

Todo:

• Update the new sync_spec.lua to install a package that has a locked dependency, and confirm that the locked dependency is indeed installed.

[mrcjkb]

Looks like luarocks is ignoring the luarocks.lock file in the install cwd.

[mrcjkb]

Blocked by luarocks/luarocks#1662