Remove application kind from pipedv1 logic

[khanhtc1202]

What this PR does:

• Remove application Kind value from app config reporter logic (pipedv1)
• Remove application Kind value from Slack notifier logic (pipedv1) - using application Labels instead
• Add TODO note to remove application Kind value from LiveStateReporter logic (pipedv1) - currently the UI is using that value to render the correct StateView component (ref: Make PipeCD control plane support plugin-arched piped #5252 (comment))

Why we need it:

The pipedv1 logic should not depend on the application Kind value.

Which issue(s) this PR fixes:

Part of #5252

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 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 28.22%. Comparing base (038a2c6) to head (0bbd96a).
Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/app/pipedv1/notifier/slack.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6008      +/-   ##
==========================================
+ Coverage   28.19%   28.22%   +0.02%     
==========================================
  Files         520      520              
  Lines       56011    56012       +1     
==========================================
+ Hits        15790    15807      +17     
+ Misses      38970    38958      -12     
+ Partials     1251     1247       -4     

Flag	Coverage Δ
.	23.26% <88.88%> (+0.03%)	⬆️
.-pkg-app-pipedv1-plugin-kubernetes	66.27% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	67.33% <ø> (ø)
.-pkg-app-pipedv1-plugin-terraform	80.26% <ø> (ø)
.-pkg-app-pipedv1-plugin-wait	35.51% <ø> (ø)
.-pkg-plugin-sdk	50.71% <ø> (ø)
.-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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[ffjlabo]

LGTM