Add gRPC api to update application deploying status

[nghialv]

What this PR does / why we need it:

Which issue(s) this PR fixes:

A part of #1369
Fixes #

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

Some issues were detected while linting go source files in your changes.

[pipecd-bot]

Code coverage for golang is 33.69%. This pull request decreases coverage by -0.07%.

File	Function	Base	Head	Diff
pkg/app/api/grpcapi/api.go	API.RegisterEvent	--	0.00%	+0.00%
pkg/app/api/grpcapi/piped_api.go	PipedAPI.ReportApplicationDeployingStatus	--	0.00%	+0.00%
pkg/app/piped/controller/controller.go	controller.reportApplicationDeployingStatus	--	0.00%	+0.00%
pkg/datastore/event.go	NewEventStore	--	100.00%	+100.00%
pkg/datastore/event.go	eventStore.AddEvent	--	100.00%	+100.00%
pkg/app/api/grpcapi/api.go	API.PushImageReference	0.00%	--	+-0.00%
pkg/datastore/imagereference.go	NewImageReferenceStore	100.00%	--	-100.00%
pkg/datastore/imagereference.go	imageReferenceStore.AddImageReference	100.00%	--	-100.00%

[nakabonne]

/lgtm

[khanhtc1202]

thank you
/approve

[pipecd-bot]

This pull request is APPROVED by khanhtc1202.

Approvers can cancel the approval by writing /approve cancel in a comment. Any additional commits also will change this pull request to be not-approved.