Fix qdrant payload schema type and add mechanism to keep types in sync

[shanbady]

What are the relevant tickets?

Closes https://github.com/mitodl/hq/issues/8567

Description (What does it do?)

This PR fixes payload index to be the correct type and also includes changes that make sure that types stay in sync with what is defined in vector_search.constants

How can this be tested?

1. checkout this branch
2. restart celery
3. run python manage.py generate_embeddings --all
4. go to your local qdrant dashboard and verify that for the learning resources collection the "certification" is now "boolean" (in the payload indexes section under the info tab)
5. open up vector_search/constants.py and change one of the payload field types for example: "course_number": models.PayloadSchemaType.INTEGER, to "course_number": models.PayloadSchemaType.KEYWORD,
6. reload celery
7. re-run the generate embeddings command
8. go back to the qdrant dashboard and note that the type associated with the field has changed.

[mbertrand]

Approving in case this is urgent, but if not it would be good to add some unit tests for the update_qdrant_indexes function

[mbertrand]

I noticed there's no unit tests for this function, would be good to add some. Could be this PR if there's no rush to get this out, otherwise in a subsequent PR.

[shanbady]

good call. added some tests

[mbertrand]

👍