Use custom piped metrics registry instead of the default one

[khanhtc1202]

What this PR does / why we need it:

• address Introducing ReportStat service to pipedservice #2181 (comment)
• fix Add piped version as label. #2182
• remove unnecessary validation in ReportStatRequest message. We should always allow the report stat to be push to the control-plane, the validation better is handled by control-plane.

Which issue(s) this PR fixes:

Fixes #2182

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

Code coverage for golang is 32.22%. This pull request decreases coverage by -0.01%.

File	Function	Base	Head	Diff
pkg/cli/cmd.go	Telemetry.PrometheusMetricsHandlerFor	--	0.00%	+0.00%

[khanhtc1202]

/hold

[pipecd-bot]

Code coverage for golang is 32.22%. This pull request decreases coverage by -0.01%.

File	Function	Base	Head	Diff
pkg/cli/cmd.go	Telemetry.PrometheusMetricsHandlerFor	--	0.00%	+0.00%

[khanhtc1202]

/hold cancel

[nghialv]

Nice.
/lgtm

[nakabonne]

awesome
/approve

[pipecd-bot]

This pull request is APPROVED by nakabonne.

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.