[Audiosharing] Avoid start sharing dialog for single device.

Issue - for LEA device with two BT addresses, when the second bud connected with
incorrect group id, we wrongly show up the start audio sharing dialog.

Fix - check there are two connected LEA valid groups before show up
start audio sharing dialog.

Bug: 347655885
Test: atest
Flag: com.android.settingslib.flags.enable_le_audio_sharing
Change-Id: Icd86ce2cfa4312c10c14906f46df324357c56990