feat: support fenl types in `Collection`

[jordanrfrazier]

FenlType::Collection currently only supports type variables, meaning we can't do map<i32, V> type signatures. We should refactor the Collection type to accept FenlTypes instead of just type vars, then clean up the parsing and inference code around that.

Tasks:

• [x] Support map<k,v> in type inference
• [ ] Support DataType::Map in merge (spread operation)
  • [x] Unlatched (https://github.com/kaskada-ai/kaskada/pull/529)
  • [ ] Latched
• [ ] Support DataType::Map in first/last aggregations
  • [x] non-windowed https://github.com/kaskada-ai/kaskada/pull/540
  • [ ] since window
  • [ ] sliding window
• [x] Support list<e> in type inference https://github.com/kaskada-ai/kaskada/pull/562
• [ ] Support DataType::List in merge (spread operation)
• [ ] Support DataType::List in aggregations
  • [x] (non-windowed) First/Last https://github.com/kaskada-ai/kaskada/pull/592
• [ ] List construction using collect function
  • [x] Doc: https://docs.google.com/document/d/1P6sogDYfq31n3LXe3WViDcHWGBfHRxNZwd1znjmagQk/edit
  • [x] Record Types https://github.com/kaskada-ai/kaskada/pull/602
  • [x] Primitive types https://github.com/kaskada-ai/kaskada/pull/569
  • [ ] Complex/Nested types
  • [x] Non-windowed https://github.com/kaskada-ai/kaskada/pull/569
  • [x] Since Window https://github.com/kaskada-ai/kaskada/pull/583
  • [ ] Sliding Windows
• [ ] Map construction
  • [ ] TODO: Doc
  • [ ] Primitive Types
  • [ ] Complex/Nested Types
• [ ] Brackets for access: map[key] list[index]
• [ ] Add get by key function for maps (get(key, map)) (https://github.com/kaskada-ai/kaskada/pull/532)
  • [x] Support boolean/string/primitives
  • [ ] Complex/Nested types
• [x] Add get by index for lists https://github.com/kaskada-ai/kaskada/pull/562
• [ ] Verify all normal functions interact with collection types as expected
• [ ] Support LargetUtf8
  • Not done in multiple aggregations yet
• [ ] Support Map Equality in Arrow eq_dyn kernel: https://docs.rs/arrow-ord/44.0.0/src/arrow_ord/comparison.rs
  • Easily done if the map is ordered, but trickier to do (efficiently) if not: [{f1: _, f2: _}] must still equal [{f2: _, f1: _}].
• [x] Improve map evaluators -- use GetIndex and take kernel to reduce duplication of evaluators/improve iteration
• [ ] Test on other sample datasets
• [ ] Using Dictionary types for efficient List (and Map?) aggregation
• [ ] Other functions
  • keys()
  • values()
  • entries()
  • getEntryFromKey/Value()
  • [x] list_len() https://github.com/kaskada-ai/kaskada/pull/609
  • reverse()
  • column<T: Struct, N: any>(input: list<T>, field: string) -> list<N>
    • takes a list of columns and gets the value for the field for each struct in each list, then collects them to a list<N>
  • Union Lists together
    • Having lists from multiple expressions and wanting to union them together to operate on a single list.

[jordanrfrazier]

Map and list types are not displayed correctly in the schema (see readings)