GH-877: Implement Plexus converter that can convert algebraic sealed types

[ascopes]

The implementation of this will expect users to take a 'kind' attribute on the marker for a sealed type parameter which is used via reflection to determine the concrete implementation class. Right now, we have to provide this info on each implementation via an annotation such that we can influence the behaviour that will eventually be provided for us by GH-880.

This PR also changes the documentation and plugin interface so that users will pass in a list containing all plugins now rather than having four distinct parameters for the same information. The exisiting parameters have been kept and still work the same way, but are now undocumented in the plugin guide, and are marked as deprecated-for-removal in v5.0.0.

With this change, we will be able to use sealed implementation kinds for the parameter in future changes, further supporting GH-877.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.88%. Comparing base (8625d4c) to head (ada4e83).
⚠️ Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #881      +/-   ##
==========================================
+ Coverage   92.66%   92.88%   +0.22%     
==========================================
  Files          71       72       +1     
  Lines        1975     2034      +59     
  Branches      127      131       +4     
==========================================
+ Hits         1830     1889      +59     
  Misses        104      104              
  Partials       41       41              

Files with missing lines	Coverage Δ
...protobufmavenplugin/mojo/AbstractGenerateMojo.java	100.00% <100.00%> (ø)
...fmavenplugin/plexus/SealedTypePlexusConverter.java	100.00% <100.00%> (ø)
...ufmavenplugin/plugins/BinaryMavenProtocPlugin.java	100.00% <100.00%> (ø)
...tobufmavenplugin/plugins/BinaryPluginResolver.java	75.41% <100.00%> (ø)
...tobufmavenplugin/plugins/JvmMavenProtocPlugin.java	100.00% <100.00%> (ø)
...protobufmavenplugin/plugins/JvmPluginResolver.java	86.00% <ø> (ø)
.../protobufmavenplugin/plugins/PathProtocPlugin.java	50.00% <100.00%> (ø)
...obufmavenplugin/plugins/ProjectPluginResolver.java	100.00% <100.00%> (ø)
...opes/protobufmavenplugin/plugins/ProtocPlugin.java	100.00% <ø> (ø)
...s/protobufmavenplugin/plugins/UriProtocPlugin.java	12.50% <100.00%> (ø)

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