RIAv2 async operations controller work

[sseago]

Thank you for contributing to Velero!

This includes the restore controller work for RestoreItemAction v2 implementation.

Fixes #5497

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]

It's not quite merge-ready as I still need to do some testing with real restores and real plugins, but it's otherwise ready for review.

[codecov-commenter]

Codecov Report

Merging #5993 (ef43511) into main (117d5e8) will increase coverage by 0.04%.
The diff coverage is 48.58%.

❗ Current head ef43511 differs from pull request most recent head 83a7a29. Consider uploading reports for the commit 83a7a29 to get more accurate results

@@            Coverage Diff             @@
##             main    #5993      +/-   ##
==========================================
+ Coverage   40.18%   40.23%   +0.04%     
==========================================
  Files         256      257       +1     
  Lines       23426    23820     +394     
==========================================
+ Hits         9414     9583     +169     
- Misses      13297    13493     +196     
- Partials      715      744      +29     

Impacted Files	Coverage Δ
pkg/builder/restore_builder.go	0.00% <0.00%> (ø)
pkg/cmd/server/server.go	5.30% <0.00%> (-0.15%)	⬇️
pkg/cmd/util/output/restore_describer.go	0.00% <0.00%> (ø)
pkg/persistence/object_store.go	52.35% <0.00%> (ø)
...reitemaction/v2/restartable_restore_item_action.go	63.75% <0.00%> (-3.36%)	⬇️
pkg/controller/restore_operations_controller.go	52.17% <52.17%> (ø)
pkg/controller/restore_controller.go	64.94% <62.16%> (-2.37%)	⬇️
pkg/controller/download_request_controller.go	66.66% <71.42%> (-1.56%)	⬇️
pkg/restore/request.go	100.00% <100.00%> (ø)
pkg/restore/restore.go	64.28% <100.00%> (+0.03%)	⬆️

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[sseago]

I've now tested this with the velero-plugin-example PR which has a recently-added RIAv2 plugin.