Audio V4: some legacy getSupported can return NOT_SUPPORTED

Legacy implementation through getParameter can not return a status_t.
This is problematic for
 - getSupportedChannelMasks(format)
 - getSupportedSampleRate(format)
as they should be able to return NOT_SUPPORTED if they do not support
the provided format.

In that case, allow the legacy implementation to return an empty string
that will be converted to NOT_SUPPORTED.

Test: atest VtsHalAudioV4_0TargetTest
Bug: 77307068
Change-Id: I78c37caf059885e3d33e6a308876dbc0e3ef7145
Signed-off-by: Kevin Rocard <krocard@google.com>