Add SetEnabledProviders API method for Credential Manager

Adds SetEnabledProviders API which is a SystemApi used
by Settings to set the list of enabled providers.

Test: make
Bug: 253157179
CTS-Coverage-Bug: 247549381
Change-Id: Ib215c66ab20c9b71a8d5f3d8734f229c93a4a3a2