add DictionaryEncodedStringValueIndex implementation to NestedFieldLiteralColumnIndexSupplier

[clintropolis]

Description

This PR adds an implementation to DictionaryEncodedStringValueIndex to NestedFieldLiteralColumnIndexSupplier, which is used in a handful of places for doing stuff with dictionary encoded columns, such as native search and segment metadata queries, fixing some bugs.

I also removed getIndex and hasNulls from DictionaryEncodedStringValueIndex, which were only used by tests.

There is another issue not addressed in this PR, which is that these things rely on ColumnCapabilities.hasBitmapIndexes to check if they can use indexes, which is really no longer adequate to know if something will have the type of indexes that they are going to ask for after #12388. I think in the future we might want to either update column capabilities to include all of the classes the ColumnIndexSupplier can supply, or make these callers check the ColumnIndexSupplier themselves.

This PR has:

• been self-reviewed.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• been tested in a test Druid cluster.