Add a module to fetch builds from different types of builders.

This module and its contents will replace the following functions and methods
in bisect-perf-regression.py:
  Most of DownloadCurrentBuild
  GetBuildArchiveForRevision
  GetRemoteBuildPath
  GetGSRootFolderName
  GetZipFileName
  FetchFromCloudStorage
  ExtractZip
  MaybeMakeDirectory

In this module, we want to be able to support downloading from different
places with possibly different naming conventions in a clean way.

As-is, this module works for downloading and extracting full builds that are
archived by the builders on the main waterfall. Example invocation:

$ python fetch_build.py full 9f11d3bc outdir

BUG=402669

Review URL: https://codereview.chromium.org/548233002

Cr-Commit-Position: refs/heads/master@{#297669}