Support LowCardinality and FixedString for Map Type

Why it matters

This feature enables more efficient storage and performance optimizations when using Map types with LowCardinality and FixedString keys or values. It addresses limitations of the Map type by allowing these compact and specialized data types, improving query speed and memory consumption for relevant use cases.

How to use it

Users can directly define Map columns with LowCardinality or FixedString as key or value types in table schemas or queries. For example, use Map(LowCardinality(String), FixedString(10)) in a CREATE TABLE statement to enable this functionality.