[le audio] Support multiple subgroup broadcast settings in native

In broadcast API, we added the support for multi-subgroup settings. This
is a follow-up change to add the support in JNI and native layers.

Tag: #feature
Bug: 267783231
Test: atest BluetoothInstrumentationTests
Test: manual test with broadcast assistant
Change-Id: Ia51f99b7950ae23ead5cfd344d54445e744c9591