Add missing Druid Ingest connection type

[FrankYang0529]

Why

• Add missing connection types and documentation for community providers #28790 tracks community provider hooks that take a connection but do not register a connection type or document their fields. DruidHook is on that list but it's not finished.
• DruidHook didn't declare conn_type, so "Druid Ingest" was missing from the connection type dropdown.
• Another issue is like the airflow druid_ingest_default connection test always fails. #33795. The default druid_ingest_default connection used conn_type="druid", and the hook uses conn_type as the URL scheme, so it produced druid://druid-overlord:8081/... and requests raised InvalidSchema.

How

• Declare conn_name_attr, default_conn_name, conn_type and hook_name on DruidHook, and register druid_ingest in provider.yaml.
• get_connection_type() no longer returns the hook's own conn_type as a URL scheme, so druid_ingest falls back to http. Any other conn_type still passes through, so connections that set it to https keep working.
• Create the default druid_ingest_default connection with conn_type="druid_ingest" so it builds a usable URL.

Verification

• uv run --project providers/apache/druid pytest providers/apache/druid/tests/unit -xvs
• uv run --project airflow-core pytest airflow-core/tests/unit/utils/test_db.py -xvs

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Was generative AI tooling used to co-author this PR?

• Yes - Claude Code

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