Gazelle Cabal bzlmod support

[aherrmann]

Related to tweag/rules_haskell#1864.

The goal is to be able to use Gazelle Cabal in a Bazel project with bzlmod enabled (--enable_bzlmod) and to develop and maintain Gazelle Cabal itself with bzlmod enabled.

bzlmod is the new way to manage dependencies in Bazel and the old WORKSPACE model will eventually be phased out. As such Gazelle Cabal needs to support bzlmod. Otherwise, users of Gazelle Cabal will not be able to move forward and migrate their projects to use bzlmod.

[marijetamh]

@aherrmann checking the sync, and checking the tasks as I go. Does this epic need dates or it is not priorities yet ?

[aherrmann]

Thanks for checking! No, this one is on the backlog without plans to work on it in the foreseeable future.