REF: refactor tests.indexes.base_index::TestIndex

[topper-123]

A lot of the tests in tests.indexes.base_index::TestIndexlook like they could like they could be improved to moving them to tests.indexes.common.Base and adapting subclasses as needed. This would give better test coverage.

See discussion in #49678 (comment).

[mroeschke]

Looks like these tests have been refactored in the meantime so closing