[8.19] [OpenAPI] Add --branch for 8.19 docs

[lcawl]

Relates to #4628

This PR updates the "make transform-to-openapi" and "make transform-to-openapi-for docs" commands to include the "--branch" parameter that was created in #4722. The parameter affects the resolution of URLs that use "{branch}" in table.csv.

NOTE:

• Since at this time 8.19 documentation does not exist, I've set the branch to "8.x" (e.g. https://www.elastic.co/guide/en/elasticsearch/reference/8.x/index.html) for now.
• The other yaml file updates were automatically generated by the "make transform-to-openapi" command.

[github-actions]

Following you can find the validation changes for the API you have modified.

API	Status	Request	Response
esql.query	🟢	320/320 → 314/314	0/0

You can validate this API yourself by using the make validate target.

[pquentin]

Thanks! LGTM. I've changed Makefile to use a variable to make sure we don't miss one line in the future update.