Remove Environment related APIs

[khanhtc1202]

What this PR does / why we need it:

By this PR, I did

• Remove all Environment-related APIs
• Remove unused Environment datastore
• mark Environment model as deprecated (will remove it as mentioned by issue Remove Environment concept from models #3221)

Which issue(s) this PR fixes:

Fixes #3222

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

Code coverage for golang is 32.55%. This pull request increases coverage by 0.21%.

File	Function	Base	Head	Diff
pkg/app/piped/planner/kubernetes/kubernetes.go	findUpdatedWorkloads	93.33%	100.00%	+6.67%
pkg/app/piped/planner/kubernetes/kubernetes.go	checkImageChange	30.77%	100.00%	+69.23%
pkg/app/server/grpcapi/api.go	API.ListApplications	0.00%	0.00%	+0.00%
pkg/app/server/grpcapi/grpcapi.go	getEnvironment	0.00%	--	+-0.00%
pkg/app/server/grpcapi/piped_api.go	PipedAPI.GetEnvironment	0.00%	--	+-0.00%
pkg/app/server/grpcapi/piped_api.go	PipedAPI.validateEnvBelongsToProject	91.67%	--	-91.67%
pkg/app/server/grpcapi/web_api.go	WebAPI.UpdateEnvironmentDesc	0.00%	--	+-0.00%
pkg/app/server/grpcapi/web_api.go	WebAPI.ListEnvironments	0.00%	--	+-0.00%
pkg/app/server/grpcapi/web_api.go	WebAPI.EnableEnvironment	0.00%	--	+-0.00%
pkg/app/server/grpcapi/web_api.go	WebAPI.DisableEnvironment	0.00%	--	+-0.00%
pkg/app/server/grpcapi/web_api.go	WebAPI.DeleteEnvironment	0.00%	--	+-0.00%
pkg/app/server/grpcapi/web_api.go	WebAPI.updateEnvironmentEnable	0.00%	--	+-0.00%
pkg/app/server/grpcapi/web_api.go	WebAPI.validateEnvBelongsToProject	0.00%	--	+-0.00%
pkg/datastore/environmentstore.go	environmentCollection.Kind	0.00%	--	+-0.00%
pkg/datastore/environmentstore.go	environmentCollection.Factory	0.00%	--	+-0.00%
pkg/datastore/environmentstore.go	NewEnvironmentStore	100.00%	--	-100.00%
pkg/datastore/environmentstore.go	environmentStore.Get	100.00%	--	-100.00%
pkg/datastore/environmentstore.go	environmentStore.List	84.62%	--	-84.62%
pkg/datastore/environmentstore.go	environmentStore.Delete	0.00%	--	+-0.00%
pkg/datastore/environmentstore.go	environmentStore.EnableEnvironment	0.00%	--	+-0.00%
pkg/datastore/environmentstore.go	environmentStore.DisableEnvironment	0.00%	--	+-0.00%
pkg/model/environment.go	MakeEnvironmentURL	100.00%	--	-100.00%

[nghialv]

Feel really good.
/lgtm

[knanao]

Thank you!
/approve

[pipecd-bot]

This pull request is APPROVED by knanao.

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.