DRIVERS-2549: add search index management helpers

[baileympearson]

This PR adds a new search management API to the index management spec.

Node POC: https://github.com/mongodb/node-mongodb-native/pull/3672

E2E testing of the new helpers against atlas will be implemented in DRIVERS-2630.

Please complete the following before merging:

• [x] Update changelog.
• [x] Make sure there are generated JSON files from the YAML test files.
• [x] Test changes in at least one language driver.
• [ ] Test these changes against all server versions and topologies (including standalone, replica set, sharded clusters, and serverless).