feat(aci): Add ability to create new environments in the API

[saponifi3d]

Description

This allows us to send a new environment through the API; (first step for ISWF-2363).

[github-actions]

Backend Test Failures

Failures on 102d88f in this run:

tests/sentry/incidents/endpoints/test_serializers.py::TestAlertRuleSerializer::test_environment_non_list — log

[gw0] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/incidents/endpoints/test_serializers.py:157: in test_environment_non_list
    assert serializer.is_valid(), serializer.errors
E   AssertionError: {'environment': [ErrorDetail(string='Failed to retrieve or create environment.', code='invalid')]}
E   assert False
E    +  where False = <bound method BaseSerializer.is_valid of AlertRuleSerializer(context={'organization': <Organization at 0x7f5689fcf570:...ult=AlertRuleDetectionType.STATIC, required=False)\n    extrapolation_mode = CharField(allow_null=True, required=False)>()
E    +    where <bound method BaseSerializer.is_valid of AlertRuleSerializer(context={'organization': <Organization at 0x7f5689fcf570:...ult=AlertRuleDetectionType.STATIC, required=False)\n    extrapolation_mode = CharField(allow_null=True, required=False)> = AlertRuleSerializer(context={'organization': <Organization at 0x7f5689fcf570: id=4557934580924432, owner_id=None, name...ault=AlertRuleDetectionType.STATIC, required=False)\n    extrapolation_mode = CharField(allow_null=True, required=False).is_valid