Android: Switch build scripts to use python3 (reland2)

Add wnwen@ to third_party/jinja2 to make future fixes/updates easier in
EST.

Fixed jinja2 bug that prevented _identifier.py from being detected by
build/print_python_deps.py (in patch 0002).

Original CL: https://crrev.com/c/3017583

All scripts previously using python under build/android should now use
python3 instead. Ran:

find build/android -name '*.py' -print0 |\
  xargs -0 grep 'env python' -H |\
  grep -v 'python3' -H

Bug: 1228231
Change-Id: Idc4028ebe643533afa3a13af1f55007ba1cdb7fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3071786
Auto-Submit: Peter Wen <wnwen@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Peter Kotwicz <pkotwicz@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#913020}
NOKEYCHECK=True
GitOrigin-RevId: 0cea52bf866bb93968869722174fd7c63fd31853

• OWNERS[diff]
• lexer.py[diff]
• patches/0002-jinja2-add-_identifier-to-pydeps-for-py3.patch[Added - diff]