Improve encapsulation and standardize TAG constants across the codebase

The log TAG should use the lowest visibility possible.
It should always be the first line after class declaration with an
empty line that follows it.

Bug: 394958283
Test: atest BluetoothInstrumentationTests
Flag: Exempt refactor no-op
Change-Id: I09e8a3f75a33eed4b2d5fcbc70b4347ab6ded2a9