backup/restore phases for async plugin operations

[sseago]

Thank you for contributing to Velero!

Please add a summary of your change

Adds new backup and restore phases to support async plugin operations:

• WaitingForPluginOperations
• WaitingForPluginOperationsPartiallyFailed

Does your change fix a particular issue?

Fixes #5491 #5492

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.
• [x ] Updated the corresponding documentation in site/content/docs/main.

[codecov-commenter]

Codecov Report

Merging #5710 (2abb176) into main (55873c1) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #5710      +/-   ##
==========================================
- Coverage   40.92%   40.89%   -0.03%     
==========================================
  Files         239      239              
  Lines       20630    20630              
==========================================
- Hits         8442     8437       -5     
- Misses      11571    11576       +5     
  Partials      617      617              

Impacted Files	Coverage Δ
pkg/uploader/provider/kopia.go	52.84% <0.00%> (-4.07%)	⬇️

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[anshulahuja98]

Hi @sseago, are there plans to also expose the list/names of plugins on which it is waiting?
Otherwise from the status it is difficult to debug which plugin is taking time or could potentially be down.
Is that part of intended design - if not does it make sense to add names?

[sseago]

@anshulahuja98 Yes -- this is probably something we'll end up putting in the velero describe output for backup/restore. describe already pulls from object storage to get warning/error, so this would be one more thing to pull in. That way velero describe backup --details would list the operations and their current status/progress.

[sseago]

@anshulahuja98 See #5700 -- the information available for each operation will include the following:
plugin, item ID, operation ID, and progress information for that operation.

[shubham-pampattiwar]

@sseago I believe this phase is the current phase of the schedule and not backup. Schedule phase is different from backup phase https://github.com/vmware-tanzu/velero/blob/main/pkg/apis/velero/v1/schedule_types.go#L67

[sseago]

@shubham-pampattiwar Oh, you're right The doc is wrong here -- it says that phase is the phase of the backup, but it's not, it's hte schedule phase. I'll update the comments to reflect this.

[sseago]

@blackpiglet @shubham-pampattiwar I fixed a problem with the schedule docs. The prior content was incorrect, listing Backup phases (which I modified in the first iteration of this PR), but schedules have their own independent list of phases, so I've updated the schedule doc to reflect that. If you could review again with the changes, that would be great.

[shubham-pampattiwar]

Thanks @sseago LGTM!