plugin/clientmgmt and framework refactoring for BackupItemAction v1

[sseago]

Thank you for contributing to Velero!

Please add a summary of your change

Refactors the clientmgmt and framework packages to implement the plugin versioning changes
needed for BIA v1 and overall package refactoring to support plugin versions
in different packages. This should be all that's needed to move on to
v2 for BackupItemAction. The remaining plugin types still need similar
refactoring to what's being done here for BIA before attempting a
v2 implementation.

Does your change fix a particular issue?

Fixes #(issue)

Please indicate you've done the following:

• [x ] Accepted the DCO. Commits without the DCO will delay acceptance.
• [x ] Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[sseago]

Note that this PR depends on #5263

That commit is included in this PR branch, but once it's merged and this PR is rebased, it won't be in this PR.

[codecov-commenter]

Codecov Report

Merging #5271 (4f17506) into main (94a9a7c) will decrease coverage by 0.02%.
The diff coverage is 63.85%.

@@            Coverage Diff             @@
##             main    #5271      +/-   ##
==========================================
- Coverage   40.69%   40.67%   -0.03%     
==========================================
  Files         233      233              
  Lines       20097    20121      +24     
==========================================
+ Hits         8179     8184       +5     
- Misses      11321    11338      +17     
- Partials      597      599       +2     

Impacted Files	Coverage Δ
pkg/cmd/server/server.go	6.65% <0.00%> (ø)
pkg/plugin/clientmgmt/process/client_builder.go	94.28% <ø> (ø)
pkg/plugin/clientmgmt/process/logrus_adapter.go	17.56% <ø> (ø)
...g/plugin/clientmgmt/process/restartable_process.go	0.00% <0.00%> (ø)
pkg/plugin/framework/backup_item_action.go	0.00% <ø> (ø)
pkg/plugin/framework/backup_item_action_client.go	0.00% <ø> (ø)
pkg/plugin/framework/backup_item_action_server.go	51.94% <ø> (ø)
pkg/plugin/clientmgmt/process/registry.go	27.69% <14.28%> (ø)
...kupitemaction/v1/restartable_backup_item_action.go	82.50% <58.82%> (ø)
pkg/plugin/clientmgmt/manager.go	80.00% <81.25%> (-1.33%)	⬇️
... and 9 more

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[sseago]

Initial backup and restore testing with this PR and BIA/RIA plugins (internal BIA/RIAs as well as the openshift plugins installed with OADP) has been successful. (v1) plugins are called just as before, with a plugin image built without any of the versioning-oriented plugin changes.

[sseago]

Updated to refactor plugin/framework as well. Tested this with backup/restore plugin images which do not import the new code.