Add python3-vcs2l-vcstool-shim debian package

[cottsay]

Basic Info

Info	Please fill out this column
Ticket(s) this addresses	resolves #88
Primary OS tested on	Ubuntu
Is this a breaking change?	No
Does this PR contain AI generated software?	No

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Description of contribution in a few bullet points

This sub-package presents vcs2l as a wholesale replacement for vcstool and should satisfy any existing dependencies on vcstool without requiring changes to vcs2l itself. It operates under the fact that the existing vcs2l API is similar enough to vcstool that it can simply be installed and used under that name.

When the vcs2l API deviates from vcstool enough, this commit may be reverted and the shim package dropped.

Description of how this change was tested

• Performed linting validation using pre-commit run --all
• Verified that the code passes all tests using python3 -m pytest -s -v test
• Verified that debs satisfy dependency on python3-vcstool

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 26.96%. Comparing base (a9022f0) to head (a82ddeb).

Additional details and impacted files

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##             main      #90   +/-   ##
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  Coverage   26.96%   26.96%           
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  Files          31       31           
  Lines        2240     2240           
  Branches      393      393           
=======================================
  Hits          604      604           
  Misses       1576     1576           
  Partials       60       60           

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[j-rivero]

Comparing to what we did in gazebo-release/gz_math_vendor#18 and we are generalizing in gazebo-tooling/gz_vendor#26. seems to me a different approach:

• This repo uses a package duplication approach where setup.py installs the same source files under both vcs2l/ and vcstool/ directories using package_dir mapping. This happens at building time duplicating code on disk.

• The gz_math_vendor#18 approach uses a runtime re-export shim - a small Python file that imports everything from the real module and re-exports it under the old name.

I think that use cases are quite different. Here there is a transparent aliasing for vcs command invocations. most of them hosted in bin/. In gz_*_vendor we are dealing with a Python library so we mostly prepare the terrain for the usuals "import gz_foo" or "from gz_foo import lala". A single entry point coming from a Python import.

Said that: I think that both approaches are fine taking into account the different context on both packages (one is a vendoring, another is a native)

[cottsay]

Thanks @j-rivero! I think the approach taken in Gazebo is much better. I drafted #94 implementing it, please have a look.