Types: Improve type mappings

[amotl]

About

• Consequently use upper-case type definitions from sqlalchemy.types
• Add timestamp without time zone types (scalar and array)
• On SQLAlchemy 2, map real and double{_precision} types to the
  newly introduced sqltypes.{DOUBLE,DOUBLE_PRECISION} types

All of this is intended to improve reverse type lookups / reflections.

References

• This is coming from another monkeypatch to meltano-target-cratedb.
• It is related to Types: Add method ObjectArray.as_generic #23.
• CrateDB Toolkit's SQLAlchemy monkeypatch.

Backlog

• Software tests.
• Just a short note(s) about type support within the documentation.

[amotl]

Dear @CaselIT,

may we humbly ask you to give this patch a quick review? We started to overhaul the type mapping of the CrateDB dialect the other day, and would like to conclude this patch.

Other than filling some gaps, we found that mapping database types to the uppercase type symbol variants provided by SQLAlchemy and back (i.e. using sqltypes.VARCHAR rather than sqltypes.String), offers better (reverse) type mapping behaviour with downstream frameworks like pandas, Meltano, or previous versions of Ibis and friends. Do you also think it is the right choice to do it this way?

With kind regards,
Andreas.

[CaselIT]

for reflected tables? it's fine, sqlalchemy types have as_generic so if users need to adapt the types to other db they can simply use that in the reflect event.

[amotl]

Thank you!