Metrics: Move bluetooth.proto to one place

* Move bluetooth.proto to proto/ and compile it for both Java LITE
  runtime and C++ LITE runtime so that it can be shared between Java
  and native code
* Remove redundant comments in bluetooth.proto

Bug: 33693818
Test: make, toggle Bluetooth, clearcut server-client E2E test
      adb shell dumpsys bluetooth_manager --proto-bin
      ACTS tests: BtMetricsTest, BtFunhausMetricsTest
Change-Id: I7cd5e1b4fb8fcc197272ef8161ff384e53022424