GH-877: Centralise Plexus components for consistency moving forwards

[ascopes]

GH-877 is likely to introduce new Plexus mechanisms and components, so this should be centralised in a common package prior to those changes such that we aim for consistency.

As part of this, converters will be wired in via CDI. There doesn't appear to be any good reason to not be doing this.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.66%. Comparing base (eaa8a74) to head (225bed8).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #878      +/-   ##
==========================================
- Coverage   92.67%   92.66%   -0.00%     
==========================================
  Files          71       71              
  Lines        1977     1975       -2     
  Branches      127      127              
==========================================
- Hits         1832     1830       -2     
  Misses        104      104              
  Partials       41       41              

Files with missing lines	Coverage Δ
...pes/protobufmavenplugin/mojo/MainGenerateMojo.java	100.00% <ø> (ø)
...pes/protobufmavenplugin/mojo/TestGenerateMojo.java	100.00% <ø> (ø)
...tobufmavenplugin/plexus/DigestPlexusConverter.java	96.43% <100.00%> (ø)
...rotobufmavenplugin/plexus/PathPlexusConverter.java	100.00% <100.00%> (ø)
...protobufmavenplugin/plexus/PluginConfigurator.java	100.00% <100.00%> (ø)
...protobufmavenplugin/plexus/UriPlexusConverter.java	100.00% <100.00%> (ø)

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