Implement Implicit Casting of Nested Types and Type Combination with MaxLogicalType

[mxwli]

Nested Implicit Casting Rules:
If the source type and destination type have different LogicalTypeIDs, no implicit cast is possible
If both types are Lists, an implicit cast is possible if their children have an implicit cast from src to dest. Arrays follow the same rule, but an additional check is made to make sure the arrays are of the same length
If both types are Structs, check if the field names match and then check if the matching children have an implicit cast from src to dest.
If both types are Maps, check that the key and value types have implicit casts from src to dest
Union casting seems to be completely unsupported right now, so no implicit casting is allowed.

Update: ARRAY -> LIST implicit casting has been implemented. It goes just the way you would expect it to go.

Max Logical Type Combination Rules:
Case 1:
If at least one type is nonnested,

1. if one type is ANY/RDF_VARIANT/STRING, cast to the other
2. if one can cast to the other, take the one with the lowest cost
3. if both are integral and one is signed & the other is unsigned, combine to lowest width signed integral type
4. otherwise cast to the value with a larger internalTypeOrder, as defined in types.cpp
   Case 2:
   If both types are nested, the rules are identical to implicit casting rules, but instead of checking "if the src children can implicit cast to the dst children", we check "if the src children can combine with the dst children".

[andyfengHKU]

Overall LGTM but I need to take another look