Add `vip app deploy validate` command for Custom Deployments #3202

Job	Run time
Dependaban	12s
Run tests (lts/*)	28s
Run tests (lts/-1)	24s
Verify signatures and provenance statements	59s
Run tests (current)	34s
Lint	42s
Type Checker	44s
Check formatting	30s
	4m 33s

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