Make LORIS-MRI Python installable via `pip install`

[MaximeBICMTL]

It would be nice to make LORIS-MRI Python installable with pip install. By "LORIS-MRI Python", I only mean the Python scripts and libraries. This does not include the Perl scripts, system dependencies, or LORIS data file system hierarchy.

Steps:

• Add project metadata to pyproject.toml (PR: Add LORIS-MRI PyProject project information (packaging PR 1) #1308).
• Add license file and centralize license information in pyproject.toml (PR: Centralize license information in Python code (packaging PR 2) #1310).
• Move dependencies from requirements.txt to pyproject.toml, and split production from development dependencies (PR: Move dependencies to PyProject (packaging PR 3) #1311).
• Add and configure a build backend.
• Move scripts path from environment to pyproject.toml, and possibly rename scripts (related issue: Rename some Python scripts to be more explicit #1219).

Some steps also require to update the installation and CI scripts.