[Backport 1.x] Re-add ApiGenerator #1219

Job	Run time
Integration OpenSearch (2.9.0)	8m 46s
Integration OpenSearch (2.8.0)	6m 30s
Integration OpenSearch (2.7.0)	6m 39s
Integration OpenSearch (2.6.0)	6m 33s
Integration OpenSearch (2.5.0)	6m 48s
Integration OpenSearch (2.4.1)	6m 48s
Integration OpenSearch (2.3.0)	6m 14s
Integration OpenSearch (2.2.1)	6m 37s
Integration OpenSearch (2.1.0)	7m 0s
Integration OpenSearch (2.0.1)	6m 29s
Integration OpenSearch (1.3.11)	6m 50s
Integration OpenSearch (1.2.4)	6m 19s
Integration OpenSearch (1.1.0)	6m 31s
Integration OpenSearch Unreleased	0s
	1h 28m 4s

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