Fix airflowctl date parameters rejecting every input value

[DHBhensdadia]

_python_type_from_string maps OpenAPI parameter annotations to the argparse type= callable used by auto-generated commands. datetime.date was mapped to the class itself, but argparse calls that callable with the raw string from the command line and date.__init__ expects three integers, so every value was rejected:

$ airflowctl dagrun list --partition-date-gte 2026-07-01
argument --partition-date-gte: invalid date value: '2026-07-01'

The message reads as a complaint about the format, but no input can succeed.

_is_primitive_type accepts datetime.date, and DagRunOperations.list declares partition_date_gte and partition_date_lte as datetime.date | None, so this affects the shipped CLI. The hand-written commands in dag_command.py already parse these values with date.fromisoformat; the generated path had no equivalent.

This adds iso_date_type alongside the existing json_dict_type and wires it into the mapping, so a valid value is parsed into a date and an invalid one reports the format that is actually expected.

datetime.datetime has the same root cause but is left untouched here, since #70249 and #70250 are already open against it. The remaining constructor entries (bytes, list, tuple, set) are not reachable today, as no operation is annotated with them.

related: #70232

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[boring-cyborg]

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