Add TaskSetDefinition as required configuration for ECS deployment

[khanhtc1202]

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #2011

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

The following ISSUES will be created once got merged. If you want me to skip creating the issue, you can use /todo skip command.

Details

---

1. Support loading TaskSetDefinition file with JSON format

https://github.com/pipe-cd/pipe/blob/2e0e8d0ffe9c284389ecb95c09ebbaf432b247b5/pkg/app/piped/cloudprovider/ecs/taskset.go#L35-L38

This was created by todo plugin since "TODO:" was found in 2e0e8d0 when #2021 was merged. cc: @khanhtc1202.

[pipecd-bot]

Code coverage for golang is 32.38%. This pull request decreases coverage by -0.28%.

File	Function	Base	Head	Diff
pkg/app/ops/handler/handler.go	NewHandler	--	0.00%	+0.00%
pkg/app/ops/handler/handler.go	Handler.Run	--	0.00%	+0.00%
pkg/app/ops/handler/handler.go	Handler.run	--	0.00%	+0.00%
pkg/app/ops/handler/handler.go	Handler.stop	--	0.00%	+0.00%
pkg/app/ops/handler/handler.go	Handler.handleTop	--	0.00%	+0.00%
pkg/app/ops/handler/handler.go	Handler.handleListProjects	--	0.00%	+0.00%
pkg/app/ops/handler/handler.go	Handler.handleAddProject	--	0.00%	+0.00%
pkg/app/ops/handler/handler.go	Handler.handleApplicationCounts	--	0.00%	+0.00%
pkg/app/ops/handler/handler.go	groupApplicationCounts	--	100.00%	+100.00%

[nakabonne]

Nice
/lgtm

[nghialv]

/approve

[pipecd-bot]

This pull request is APPROVED by nghialv.

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.