Ignore unsupported plugin when reporting livestate

[ffjlabo]

What this PR does:

Get only livestate-supported plugin clients when flushing the livestate.

Currently, the livestate reporter fails to report when there are some plugins that don't support the livestate feature. (e.g. wait stage).

Livestate reporter calls GetLivestate for each plugin when flushing an app.
But currently, it fails when one of them has an error, including an unimplemented status.

Why we need it:

Which issue(s) this PR fixes:

Follow #5940
Part of #5363

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 28.47%. Comparing base (d73300d) to head (ab14df5).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...app/pipedv1/livestatereporter/livestatereporter.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5942      +/-   ##
==========================================
- Coverage   28.47%   28.47%   -0.01%     
==========================================
  Files         520      520              
  Lines       56415    56410       -5     
==========================================
- Hits        16063    16060       -3     
+ Misses      39086    39084       -2     
  Partials     1266     1266              

Flag	Coverage Δ
.	23.76% <50.00%> (+0.01%)	⬆️
.-pkg-app-pipedv1-plugin-example	0.00% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes	66.42% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	67.51% <ø> (ø)
.-pkg-app-pipedv1-plugin-wait	35.51% <ø> (ø)
.-pkg-plugin-sdk	48.86% <ø> (-0.37%)	⬇️
.-tool-actions-gh-release	19.23% <ø> (ø)
.-tool-actions-plan-preview	25.30% <ø> (ø)
.-tool-codegen-protoc-gen-auth	0.00% <ø> (ø)

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[t-kikuc]

LGTM

When livestatereporter has performance issues, let's improve.

[t-kikuc]

When needed in the future (not now),
let's remove such plugins from pluginClis, err := r.pluginRegistry.GetPluginClientsByAppConfig(cfg.Spec) by like r.pluginRegistry.markPluginAsLiveStateUnsupported(xxx) to reduce unnecessary gRPC calls.

[Warashi]

👍🏻