Add previously released API to hwbinder-stubs-docs

This is needed because Metalava is going to be strict about requiring a
previously released API to ensure that flagged APIs work correctly.
The `hwbinder-stubs-docs` module is a subset of the system API and
relies on the `system-api-stubs-docs-non-updatable` performing any
compatibility checks. So, this provides the same previously released
API as `system-api-stubs-docs-non-updatable` to ensure consistent
handling of flags but disables the compatibility checks to avoid
duplicating the work.

Flag: EXEMPT build change to improve flag support
Bug: 425309457
Test: TH
Change-Id: I5c7ba41ebc4eeb53eefd24663e6d564752335bc0