Create an Android Lint rule to find guarded log invocations

The Bluetooth stack sets a process default log level, which allows the
Android Log framework to properly enforce wheth a log invocation fires
based on the set log level for the tag. You do not need to guard
individual log invocations anymore.

This lint rule looks for log lines inside conditionals (if, else if, or
even else), where the conditionals use variables that appear to be log
enforcement variables as part of their logic. Errors are generated for
those usages. Because this is mostly name based, this is very much best
effort, and will have to be updated as patterns in the stack evolve.
This was able to find all the violations in the stack that existed
before our refactor though.

Usages of Log.isLoggable() in conditionals are reduced to warnings, as
there are a few valid usages to prevent expensive log operations in
code. In general, we expect these usages to be minimal and hope
developers will consider altering log statements to avoid usages.

Run this lint rule together with others using `m Bluetooth-lint`.
Results are available in txt/xml/html format in the build output
artifacts. See the README for more details.

Tag: #feature
Bug: 315046089
Flag: EXEMPT, tooling change
Test: atest BluetoothLintCheckerTest --host
Change-Id: I175f908f97567ed6638af6026f4caf83acd57e60