shared/bap: fix crash unregistering media endpoint while streaming

shared/bap: fix crash unregistering media endpoint while streaming

Always free BAP stream in bt_bap_stream_release if it is not attached to
a client session, simplifying the cleanup.

Fixes the following ASAN crash is observed when media endpoint is
unregistered (stopping sound server) while streaming from remote BAP
client:

ERROR: AddressSanitizer: heap-use-after-free on address 0x60b0000474d8
READ of size 8 at 0x60b0000474d8 thread T0
    #0 0x7a27c6 in stream_set_state src/shared/bap.c:1227
    #1 0x7aff61 in remove_streams src/shared/bap.c:2483
    #2 0x71d2d0 in queue_foreach src/shared/queue.c:207
    #3 0x7b0152 in bt_bap_remove_pac src/shared/bap.c:2501
    #4 0x463cda in media_endpoint_destroy profiles/audio/media.c:179
    ...
0x60b0000474d8 is located 8 bytes inside of 112-byte region
freed by thread T0 here:
    #0 0x7f93b12b9388 in __interceptor_free.part.0 (/lib64/libasan.so.8+0xb9388)
    #1 0x7a0504 in bap_stream_free src/shared/bap.c:972
    #2 0x7a0800 in bap_stream_detach src/shared/bap.c:989
    #3 0x7a26d1 in bap_stream_state_changed src/shared/bap.c:1208
    #4 0x7a2ab4 in stream_set_state src/shared/bap.c:1252
    #5 0x7ab18a in stream_release src/shared/bap.c:1985
    #6 0x7c6919 in bt_bap_stream_release src/shared/bap.c:4572
    #7 0x7aff50 in remove_streams src/shared/bap.c:2482
    ...
previously allocated by thread T0 here:
    #0 0x7f93b12ba6af in __interceptor_malloc (/lib64/libasan.so.8+0xba6af)
    #1 0x71e9ae in util_malloc src/shared/util.c:43
    #2 0x79c2f5 in bap_stream_new src/shared/bap.c:766
    #3 0x7a4863 in ep_config src/shared/bap.c:1446
    #4 0x7a4f22 in ascs_config src/shared/bap.c:1481
    ...