[FEATURE REQUEST]: Support indexes on nested maps

[andrei-ionescu]

Feature requested

As a data engineer, data scientist, developer, I want to be able to use indexing with maps, in order to improve query performance.

Acceptance criteria

• Create index over a nested map (keys & values)
• Use the index in the filter and joins in all use cases (append only, delete only, hybrid scans, etc)

Success criteria

• Index created properly
• Index used in the filters and joins

Additional context**

This is part of the #347.