Add gn builds for main/shim

This adds GN builds for main/shim, along the way adding some fixes:
* Add message_loop_thread_bridge_header to use Rust's message loop
* Add some missing includes
* Build files for dumpsys
* Add gd/hci gn build

Bug: 176847216
Tag: #refactor
Test: atest --host bluetooth_test_common

Change-Id: Ide1edbb70076c4dcc4a4e6ee41303a9e315d52af