Implement psdk-use subcommands

[Aelysya]

Description

This PR adds the subcommands of psdk-use

• mr [ID]
• latest
• commit [SHA1]
• version [VERSION]

It allows using the CLI to quickly checkout a branch/commit/version when inside a psdk project.

closes #17

Tests to perform

• Using the command psdk-use help displays a list of available commands and their use
• Using any of the commands outside of a psdk project results in an error message saying "Not in a project".
• All 4 commands resolve to the correct branch/commit/version specified when the given argument is valid.
• After a successful checkout, a message describing the current state of the repository is shown (commit ref and name)
• All 4 commands display an error when the given argument is invalid.

[NuriYuri]

Did the tests (review needs to be done). Everything works.
We can open a new issue:

When we use psdk-use latest then psdk-use studio then psdk-use latest. The command do not use the opportunity to simply rename `pokemonsdk_old` to `pokemonsdk` if that's a valid git repository pointing to the actual repo

I'll do the review when I can and then add comments if I see anything.

PS: I tried both short commit ID and long commit ID.

[NuriYuri]

Looks good.

While reading the code I thought that my own PSDK project is not a git repository, that means my test do not cover the case when a project uses pokemonsdk as a submodule.