kleaf: init_ddk: Add support to download files

* This change introduces a new function to download files, by
  contstructing a valid URL using information like build_id,
  build_target and remote_filename.

* Due to hermeticity reasons, the python toolchain lacks valid
  certificates to verify the downloads, for that reason, the downloads
  rely on the host toolchain just for these.

* To avoid spam during these calls, and in case of any error only the
  last line of the stacktrace is printed in case of any exception.

Bug: 328770706
Change-Id: I80fb8867a6d009043d0d2bb376bf0c2557774e17
Signed-off-by: Ulises Mendez Martinez <umendez@google.com>
4 files changed