LE Audio: Use Read Multiple for initial ASE read

For some earbuds this can reduce LE profile connection time by 300ms

Devices that don't support EATT, might not support Read Multiple
Variable Length. For them, we would simulate "Read Multiple" in stack.

Test: atest bluetooth_le_audio_client_test
Flag: le_ase_read_multiple_variable
Bug: 352085435
Bug: 296836982
Change-Id: I5aeb3178115eb02e503a9f18ca4cf11fe14dec7f