LeAudio: Add missing direction contexts for metadata passing

The group and device APIs were getting single combined stream context type
which caused unnecessary context mixing for a single direction in a
stream. With this change, the groups and the devices always get the metadata
for each direction but at the end, the ASEs will get only the proper direction
metadata when stream is enabled (or metadata updated).

This also solves the problem of the missing reconfiguration context, i.e. which
direction metadata should be passed to the group and device after
previous stream gets stopped.

Last but not least, the mixed content can force additional volume level
changes if the remote device keeps each stream type volume on its end
and restores them when the context changes (instead of realying on the
central device to restore the proper volume).

Bug: 247659576
Tag: #feature
Test: atest BluetoothInstrumentationTests
Test: atest --host bluetooth_le_audio_client_test bluetooth_le_audio_test --no-bazel-mode
Change-Id: I37b0175a55c787e18547b9612a142bfaae11b678