Fix up files to compile on Linux

Fix up all the .gn files so that they will compile on Linux. In order to
compile with GN, there is a new dependency on common-mk (currently part
of chromiumos/platform2) and most third-party libraries now use
pkg-config to include and link. As a result, all build paths are
prefixed with //bt now.

In addition, also disable building non standard codecs temporarily (i.e.
ldac, aptx, aac). We will add a way to enable them via build flags later
but we're disabling them entirely for now.

Bug: 176847216
Bug: 176846220
Tag: #refactor
Test: run --host bluetooth_test_gd
Test: run --host bluetooth_test_common
Change-Id: I85e5f8bd64c9ad074537cdd1393d373d5644aca0