releasetools: Switch to Python logging.

Converts the following files to Python logging.

add_img_to_target_files.py
blockimgdiff.py
build_image.py
check_ota_package_signature.py
common.py
img_from_target_files.py
make_recovery_patch.py
ota_from_target_files.py
sparse_img.py
verity_utils.py

This separates logging outputs from normal outputs, and allows easier
switching between different verbosity levels. It also supports adjusting
logging config via environment variable (LOGGING_CONFIG).

Test: `m dist`
Test: `python -m unittest discover build/make/tools/releasetools`
Change-Id: Idfc3f7aff83e03f41f3c9b5067d64fd595d5192d