Extend function features to allow new repo types

[RexWzh]

Main Changes

1. Lean Version: Use string for lean_version instead of a commit hash. Postpone the initialization of the Lean4 repository.
2. Cache: Update cache.get and cache.store for increased flexibility.
3. Repository Type: Extend function capabilities to support new repository types, such as _to_commit_hash, normalize_url, get_latest_commit, and url_to_repo, each with tests to ensure reliability.

Progress

Implementation plan for the new feature:

• [x] Integrate gitpython into the project (#188).
• [ ] Enhance function capabilities to support new repo types (current PR).
• [ ] Add two new repository types for tracing and interaction (#179).

[RexWzh]

Thank you @yangky11 , for your thorough review of most of the work.

The remaining tasks are straightforward after this PR merged.

Two notes to mention:

1. The test case remote_example_url currently uses my cloned URL on gitee.com, which will not change, but can be replaced if needed.
2. As git.Repo requires a directory, I plan to place them in .cache/lean_dojo/repos in the last PR.

For compatibility, the cache directory looks like:

❯ tree -L 2 lean_dojo
lean_dojo
├── leanprover-community-aesop-79fb157c6a5061190d169535f8e5cb007914a82e
├── leanprover-community-batteries-d2b1546c5fc05a06426e3f6ee1cb020e71be5592
├── repos
│   ├── rexzong-lean4-example-3f8c5eb303a225cdef609498b8d87262e5ef344b
│   └── testrepo-lean4-example-3f8c5eb303a225cdef609498b8d87262e5ef344b
├── yangky11-lean4-example-3f8c5eb303a225cdef609498b8d87262e5ef344b
└── yangky11-lean4-example-7b6ecb9ad4829e4e73600a3329baeb3b5df8d23f

11 directories, 0 files

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Pytest result

[RexWzh]

merge to #179