Treat non-sensitive-only as true and always mask sensitive values in public api's

[pratyush0325]

Summary

This PR updates the behavior of the public config API to ensure sensitive configuration values are never exposed.

Changes

• Always mask sensitive configuration values, even when expose_config=True
• Treat the deprecated value non-sensitive-only as True
• Update tests to reflect the masking behavior
• Update documentation and references to reflect the new config behavior
• Added corresponding newsfragment (59880.bugfix.rst)

Tests

• Updated unit tests to ensure sensitive values are always masked
• Verified behavior for:
  • expose_config=True
  • expose_config=False
  • expose_config=non-sensitive-only

Closes: #59860

---

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In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
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In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in airflow-core/newsfragments.

[boring-cyborg]

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[potiuk]

Let's see if CI agrees !

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.