Support Annotated values around None and Union types

[jptrindade]

At the moment we only partially support Annotated around None or Union types, the simpler and more common cases. However, we are not parsing correctly nested unions and annotated optional values.

Here are some examples that we wish to support:

 import typing
import inmanta.ast.type
from inmanta import plugins
from inmanta import ast


dsl_type: ast.type.Type = plugins.to_dsl_type(int | typing.Annotated[str | None, "some-annotation"], None, None)
# assert isinstance(dsl_type, ast.type.NullableType) # fails

dsl_type2: ast.type.Type = plugins.to_dsl_type(int | typing.Annotated[str | float, "some-annotation"], None, None)
assert isinstance(dsl_type2, ast.type.Union)
# assert len(dsl_type.types) == 3  # fails
assert isinstance(normalize_dsl_type(dsl_type2), ast.type.Union)
# assert len(normalize_dsl_type(dsl_type2).types) == 3  # fails

Slack thread: https://inmanta.slack.com/archives/CKRF0C8R3/p1738855256781129