atlasaction: refactor `monitor/schema` #1403

Job	Run time
migrate-down	28s
golangci-lint	18s
monitoring	34s
migrate-test	13s
schema-apply (lint-review)	7s
schema-plan	16s
schema-apply (on-the-fly, true)	8s
schema-plan-approve	0s
schema-apply (remote-repo, atlas://atlas-action/plans/20240910183610, atlas://atlas-action?tag=e2e)	8s
schema-push	7s
schema-test	8s
schema-apply (local-plan, file://20240910173744.plan.hcl)	15s
schema-apply (multiple-envs, file://20240910173744.plan.hcl)	17s
shim	11s
schema-apply (legacy, v0.27.0, true)	17s
shim-e2e	6s
unit-tests	1m 12s
	4m 45s

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