Update API generator to use new OpenAPI specification #671

Job	Run time
YAML Tests (Released OpenSearch) (2.11.1)	3m 28s
YAML Tests (Released OpenSearch) (2.10.0)	3m 28s
YAML Tests (Released OpenSearch) (2.8.0)	3m 19s
YAML Tests (Unreleased OpenSearch) (1.x)	3m 23s
YAML Tests (Released OpenSearch) (2.6.0)	3m 12s
YAML Tests (Unreleased OpenSearch) (2.x)	9m 27s
YAML Tests (Released OpenSearch) (2.4.1)	3m 15s
YAML Tests (Unreleased OpenSearch) (main)	8m 51s
YAML Tests (Released OpenSearch) (2.2.1)	3m 6s
YAML Tests (Released OpenSearch) (2.0.1)	3m 21s
YAML Tests (Released OpenSearch) (1.3.14)	3m 23s
YAML Tests (Released OpenSearch) (1.2.4)	3m 16s
YAML Tests (Released OpenSearch) (1.1.0)	2m 46s
	54m 15s

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