Change type definition for DeployTargetsByPlugin

[ffjlabo]

What this PR does:

sd title

Why we need it:

We can't use type google.protobuf.ListValue because Firestore SDK doesn't treat the type.

Which issue(s) this PR fixes:

Part of #4980 #5252
Follow #5553 #5554

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 3.92157% with 49 lines in your changes missing coverage. Please review.

Project coverage is 26.43%. Comparing base (1e2231f) to head (e975b7b).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/app/pipectl/cmd/migrate/database.go	0.00%	18 Missing ⚠️
...p/pipedv1/plugin/kubernetes/deployment/rollback.go	0.00%	6 Missing ⚠️
pkg/model/application.go	0.00%	6 Missing ⚠️
pkg/model/deployment.go	0.00%	6 Missing ⚠️
...g/app/pipedv1/plugin/kubernetes/deployment/sync.go	33.33%	3 Missing and 1 partial ⚠️
pkg/datastore/datastoretest/datastore.mock.go	0.00%	4 Missing ⚠️
pkg/datastore/applicationstore.go	0.00%	2 Missing ⚠️
pkg/app/piped/trigger/deployment.go	0.00%	1 Missing ⚠️
pkg/app/pipedv1/trigger/deployment.go	0.00%	1 Missing ⚠️
pkg/app/server/grpcapi/api.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5555      +/-   ##
==========================================
- Coverage   26.44%   26.43%   -0.02%     
==========================================
  Files         465      465              
  Lines       49862    49901      +39     
==========================================
+ Hits        13188    13189       +1     
- Misses      35620    35657      +37     
- Partials     1054     1055       +1     

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