Add `vip app deploy validate` command for Custom Deployments #3204

Job	Run time
Lint	35s
Type Checker	25s
Check formatting	27s
Dependaban	8s
Verify signatures and provenance statements	48s
Run tests (lts/*)	35s
Run tests (lts/-1)	43s
Run tests (current)	46s
	4m 27s

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