cmd/atlas/internal/sqlparse: move parsers out #1974

Job	Run time
lint	32s
generate-cmp	49s
integration	34s
cli	2m 59s
unit (1.22)	19s
dialect-integration / integration-maria107	2m 48s
dialect-integration / integration-mysql57	2m 45s
dialect-integration / integration-mysql56	2m 45s
dialect-integration / integration-mysql8	2m 56s
dialect-integration / integration-maria102	2m 58s
dialect-integration / integration-maria103	2m 48s
dialect-integration / integration-postgres10	3m 7s
dialect-integration / integration-postgres11	3m 4s
dialect-integration / integration-postgres-ext-postgis	3m 14s
dialect-integration / integration-postgres12	3m 2s
dialect-integration / integration-postgres13	3m 9s
dialect-integration / integration-postgres14	3m 5s
dialect-integration / integration-sqlite	2m 20s
dialect-integration / integration-postgres15	3m 4s
dialect-integration / integration-tidb6	3m 25s
dialect-integration / integration-cockroach	2m 55s
dialect-integration / integration-tidb5	3m 21s
	55m 59s

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