[OpenAPI] Edit search API summaries

[lcawl]

Relates to #2635

This PR edits the summaries for a subset of search APIs, such that they more closely align with our style recommendations and the titles from https://www.elastic.co/guide/en/elasticsearch/reference/master/search.html

Reviewer notes

Since the openAPI document is too big for previews and not hooked into buildkite previews yet, if reviewers are wanting to review the strings, they all appear in the output/openapi/elasticsearch-openapi.json file. The serverless file in that folder is the same or smaller subset so it's not necessary to compare both output for the purposes of these text edits.

[github-actions]

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

API	Status	Request	Response
clear_scroll	🟢	17/17	17/17
close_point_in_time	🟢	7/7	7/7
field_caps	🟢	63/63	63/63
msearch_template	🟢	1/1	1/1
open_point_in_time	🟢	7/7	7/7
rank_eval	⚪	Missing test	Missing test
render_search_template	🟢	1/1	1/1
search_template	🟢	2/2	1/1

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

[github-actions]

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

API	Status	Request	Response
clear_scroll	🟢	17/17	17/17
close_point_in_time	🟢	7/7	7/7
field_caps	🟢	63/63	63/63
msearch_template	🟢	1/1	1/1
open_point_in_time	🟢	7/7	7/7
rank_eval	⚪	Missing test	Missing test
render_search_template	🟢	1/1	1/1
search_template	🟢	2/2	1/1

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

[github-actions]

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

API	Status	Request	Response
async_search.delete	🟢	4/4	4/4
async_search.get	🟢	6/6	6/6
async_search.status	🟢	3/3	3/3
async_search.submit	🟢	7/7	7/7
clear_scroll	🟢	17/17	17/17
close_point_in_time	🟢	7/7	7/7
field_caps	🟢	63/63	63/63
knn_search	🟢	4/4	4/4
msearch_template	🟢	1/1	1/1
open_point_in_time	🟢	7/7	7/7
rank_eval	⚪	Missing test	Missing test
render_search_template	🟢	1/1	1/1
search_mvt	⚪	34/34	Missing test
search_shards	🟢	7/7	7/7
search_template	🟢	2/2	1/1
search	🔴	2213/2273	2254/2255
termvectors	🟢	8/8	8/8

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

[github-actions]

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

API	Status	Request	Response
async_search.delete	🟢	4/4	4/4
async_search.get	🟢	6/6	6/6
async_search.status	🟢	3/3	3/3
async_search.submit	🟢	7/7	7/7
clear_scroll	🟢	17/17	17/17
close_point_in_time	🟢	7/7	7/7
field_caps	🟢	63/63	63/63
knn_search	🟢	4/4	4/4
msearch_template	🟢	1/1	1/1
open_point_in_time	🟢	7/7	7/7
rank_eval	⚪	Missing test	Missing test
render_search_template	🟢	1/1	1/1
search_mvt	⚪	34/34	Missing test
search_shards	🟢	7/7	7/7
search_template	🟢	2/2	1/1
search	🔴	2213/2273	2254/2255
termvectors	🟢	8/8	8/8

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