Resolve team scoped spelling of per-key secrets-backend-kwarg options as sensitive

[abhishekmauryaKsolves]

closes #71037

What

_is_per_key_sensitive_option and _mask_per_key_sensitive_options in
airflow-core/src/airflow/api_fastapi/core_api/services/public/config.py
matched literal section names (secrets, workers) only. A team scoped
spelling of the same option -- the [<team>=secrets] config-file section,
or the AIRFLOW__<TEAM>___SECRETS__BACKEND_KWARG__* environment variable,
both of which are reported under a section named after the team -- was
never recognised as sensitive.

Not exploitable today, since _get_custom_secret_backend is not team-aware
yet. But the gap becomes live the moment secrets backends gain team scoping,
and at that point it fails open: a team's backend credentials would be
returned in full by GET /config.

How

Both functions now resolve the section to its base section via
base_section_name -- the same helper AirflowConfigParser.is_sensitive_option
already uses for registered sensitive options (introduced in #70755) --
before deciding whether the option is sensitive.

• _is_per_key_sensitive_option: looks up the prefix under
  base_section_name(section) instead of section.
• _mask_per_key_sensitive_options: now iterates every section actually
  present in conf_dict (rather than only the literal secrets / workers
  keys) and resolves each one to its base section before matching. This
  also covers the team scoped env var case, since conf.as_dict already
  reports it under the team-derived section.

Testing

Added TestTeamScopedPerKeyBackendKwargMasking in
airflow-core/tests/unit/api_fastapi/core_api/routes/public/test_config.py,
covering:

• GET /config redacts a team scoped per-key option under both the
  secrets and workers team scoped sections, while a non-sensitive
  option in the same response stays untouched.
• GET /config/section/{section}/option/{option} redacts a team scoped
  per-key option the same way it redacts the non-team-scoped one.

Full test_config.py suite run clean: 3377 passed, 0 failed.