Make index settings blocks stringified

[stevejgordon]

Raised in elastic/elasticsearch-net#7714, it appears that the possible block values should all be stringified as they are each produced as an APIBlock (see server code).

This PR updates each possible block option to support the stringified value when getting index settings.

[Anaethelion]

LGTM

[github-actions]

Following you can find the validation results for the APIs you have changed.

API	Status	Request	Response
indices.add_block	🟢	2/2	2/2
indices.analyze	🟢	20/20	20/20
indices.clear_cache	🟢	4/4	4/4
indices.clone	🟢	4/4	4/4
indices.close	🟢	44/44	44/44
indices.create_data_stream	🟢	25/25	25/25
indices.create	🔴	740/744	744/744
indices.data_streams_stats	🟢	4/4	4/4
indices.delete_alias	🟢	15/15	15/15
indices.delete_data_lifecycle	🟠	Missing type	Missing type
indices.delete_data_stream	🟢	27/27	27/27
indices.delete_index_template	🟢	1/1	1/1
indices.delete_template	🟢	9/9	9/9
indices.delete	🟢	104/104	104/104
indices.disk_usage	🟢	3/3	3/3
indices.downsample	🟢	1/1	1/1
indices.exists_alias	🟢	36/36	36/36
indices.exists_index_template	⚪	Missing test	Missing test
indices.exists_template	🟢	15/15	15/15
indices.exists	🟢	39/39	39/39
indices.explain_data_lifecycle	🟠	Missing type	Missing type
indices.field_usage_stats	🟢	5/5	5/5
indices.flush	🟢	9/9	9/9
indices.forcemerge	🔴	4/4	3/4
indices.get_alias	🔴	82/82	70/82
indices.get_data_lifecycle	🟠	Missing type	Missing type
indices.get_data_stream	🟢	12/12	12/12
indices.get_field_mapping	🔴	15/15	14/15
indices.get_index_template	🔴	17/18	14/18
indices.get_mapping	🔴	64/64	62/64
indices.get_settings	🔴	54/54	52/54
indices.get_template	🟢	30/30	30/30
indices.get	🟢	52/52	52/52
indices.migrate_to_data_stream	⚪	Missing test	Missing test
indices.modify_data_stream	⚪	Missing test	Missing test
indices.open	🟢	17/17	17/17
indices.promote_data_stream	⚪	Missing test	Missing test
indices.put_alias	🟢	53/53	53/53
indices.put_data_lifecycle	🟠	Missing type	Missing type
indices.put_index_template	🔴	37/43	43/43
indices.put_mapping	🔴	72/73	73/73
indices.put_settings	🔴	52/54	54/54
indices.put_template	🔴	40/46	46/46
indices.recovery	🟢	10/10	10/10
indices.refresh	🟢	208/208	208/208
indices.reload_search_analyzers	🟢	2/2	2/2
indices.resolve_index	🟢	6/6	6/6
indices.rollover	🟢	26/26	26/26
indices.segments	🔴	6/6	5/6
indices.shard_stores	🔴	5/5	4/5
indices.shrink	🟢	4/4	4/4
indices.simulate_index_template	🔴	6/7	7/7
indices.simulate_template	🔴	4/5	4/5
indices.split	🟢	11/11	11/11
indices.stats	🔴	100/100	34/99
indices.unfreeze	🟢	1/1	1/1
indices.update_aliases	🟢	22/22	22/22
indices.validate_query	🟢	7/7	7/7

You can validate these APIs yourself by using the make validate target.