Add Cloud SQL Proxy as server and ops sidecar

[khanhtc1202]

What this PR does / why we need it:

Add cloud-sql-proxy container as server and ops sidecar to enable connect to GCP Cloud SQL using Cloud SQL Auth proxy.

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

Code coverage for golang is 32.08%. This pull request increases coverage by 0.16%.

File	Function	Base	Head	Diff
pkg/app/piped/eventwatcher/eventwatcher.go	modifyText	--	86.67%	+86.67%
pkg/app/piped/eventwatcher/eventwatcher.go	watcher.commitFiles	0.00%	0.00%	+0.00%
pkg/cache/memorycache/lru_cache.go	LRUCache.Get	66.67%	100.00%	+33.33%
pkg/config/event_watcher.go	EventWatcherEvent.Validate	73.68%	71.43%	-2.26%
pkg/regexpool/regexpool.go	Pool.Get	87.50%	93.75%	+6.25%

[nghialv]

/lgtm

[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.