Use the build_config.h in libchrome.

As preparation to merge libmojo into libchrome,
this CL starts to use same build_config.h.
The biggest side effect is, now libmojo is built with OS_CHROMEOS
rather than OS_ANDROID, as libchrome is built so.

Along with the change;
- base/base_paths_posix is introduced and replacing base_paths_android,
  with small modification (dropping several paths).
  Effectively no diff, because FILE_EXE,MODULE are conceptually
  same implementation.
- base/files/file_util_android.cc is removed. GetShmemTempDir()
  is provided by libchrome.
- base/message_pump_android is dropped, as it isn't used.
- base/trace_event/* is dropped. These aren't used.
- Added defined(__ANDROID__) into "#if defined(OS_ANDROID)" in mojo
  to keep the same behavior.
- Removed unnecessary JNI proxy generation code, and its .java files.
  Specifically, those files were not included in .jar library,
  so no runtime code should have reached to them.

Bug: 73606903
Test: Apply similar patch to N, and tested on DUT. Treehugger.
      In case of crash, got the correct stack trace.
Change-Id: I2292290788a62e1c6b005595d442433e26e879de
23 files changed