audio: Query minimum buffer size before opening streams

The proper way to obtain the minimum buffer size when
opening a stream is to retrieve it from the patch. Thus,
a patch must be established prior to opening a stream.
This step was often skipped by VTS tests, they were
providing a fixed stream buffer size which might not
work for all HAL module implementations.

Created a helper class `StreamFixture` which handles
all necessary steps for opening a stream. Overhauled
tests to use this class.

Also, remove special treatment of remote submix devices
by ModuleConfig.

Bug: 300735639
Test: atest VtsHalAudioCoreTargetTest
Change-Id: Ic51d603d2bb8ff0fd62434bd16fc02c51326fc42