Format BufferHub{Buffer,Metadata}.{h,cpp} to match libui style

1/ Run clang-format
2/ Rename variables to use camel case
3/ 100 column per line
4/ Rename DetachedBuffer to BufferHubBuffer

Bug: 68273829
Bug: 112010261
Bug: 112940221
Test: BufferHubMetadata_test, buffer_hub-test
Change-Id: Iaf0dbbe797daf8b61864dc2e3ea1693703ef9d7f