fix: Use 'req@url' syntax to install from remote VCS

[matthewfeickert]

Use 'req@url' syntax when using pip to install from a remote git repository over 'url#egg=req' to avoid the use of #egg= fragments with a non-PEP 508 name. This will be required in pip v25.0+.

• c.f. https://github.com/pypa/pip/pull/11617 for more details.

Also use pip's git+https VCS scheme over git+git as recommended in the pip docs on VCS Support:

The use of git, git+git, and git+http schemes is discouraged. The former two use the Git Protocol, which lacks authentication, and HTTP is insecure due to lack of TLS based encryption.

[matthewfeickert]

@oshadura this is ready for review. Let me know if you have any questions. :+1:

[oshadura]

Many thanks!