build: LOG_TAG consistency, include order, build fixes

Fix the order of includes across a bunch of files, and declare LOG_TAG
at the top of every file in which it is used.

Consistently use bt_ as a LOG_TAG prefix.
Fix issues with LOG macro usage.
Remove unused includes and double-includes (when in related .h)

Add includes as necessary to compile cleanly (problems surfaced by
reordering includes)

Change-Id: Ic55520c8302b06bbc1942c10c448b20844669da6