Complex scalars support

[1st1]

for querying / filtering / casting -- the whole flow

[1st1]

As well as complex scalars -- arrays, arrays of tuples with nested arrays, etc

[vpetrovykh]

Some complex scalar tests are here: https://github.com/geldata/gel-python/pull/659

The tests that fetch the scalar values from the database using QB work. The tests that edit values fail.

[vpetrovykh]

No separate tests for enums yet.

[1st1]

@vpetrovykh Can you add a test for enum?

@elprans we need to fix values editing - moving this to high pri

[vpetrovykh]

Added a couple of tests for enums: #659 test_modelgen_enum_01 and test_modelgen_enum_02 for reading and creating enum values.

[1st1]

Complex scalars still need work, iirc -- there's no validation for them