Refactor: extract `BaseScan` and `ManifestGroupPlanner` #8951

Job	Run time
cibw-dev-env-smoke-test	25s
integration-test-gcs	1m 30s
lint-and-unit-test (3.14)	2m 30s
lint-and-unit-test (3.12)	3m 20s
lint-and-unit-test (3.13)	3m 8s
integration-test-s3	1m 12s
lint-and-unit-test (3.10)	3m 16s
integration-test-adls	1m 16s
lint-and-unit-test (3.11)	2m 59s
integration-test	11m 5s
integration-coverage-report	27s
	31m 8s

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