Broadcaster: Fix atest running wrong unit tests

When calling:
  atest --host bluetooth_test_broadcaster
atest tool actually runs:
  bluetooth_test_broadcaster_sm
This is most likely due to some fuzzy search algorithm in atest.
Making names more distinct fixes the issue.

Bug: 240145685
Tag: #feature
Test: atest bluetooth_test_broadcaster --no-bazel-mode
Change-Id: I0bcfcc83f0bdac1ce7803455abe427e89c34fa4f