Allow version = latest for Maven, Git and PyPI locations

[lfvjimisola]

Should perhaps be able to specify:

stable/unstable vs release/pre-release

• latest-stable: stable
• latest-unstable: unstable
• latest-all: stable and unstable

for

• maven_location: maven_artifact has support for it already: https://github.com/hamnis/maven-artifact/blob/main/src/maven_artifact/resolver.py#L38
• pypi_location: we have to implement it for pypilocation (I think that we get all versions with PyPI Simple API)
• git

[lfvjimisola]

During an internal LFV meeting we decided to postpone this (although everything is more or less implmented).

We are not sure about the functionality (latest, latest-stable, latest-unstable).

Shall we use something like PEP440 for Python, Version Ranges for Maven etc.

Or shall we simply just say that the version needs to be explicit and it can then be handled using e.g. environment variables (renovate)?