Adds `strutil.template(...)` function.

R=nodir@chromium.org, tandrii@chromium.org

Change-Id: Id1a160c02bb63647cbc5215347d6024bc5d14ad1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1899569
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>
Commit-Queue: Nodir Turakulov <nodir@chromium.org>
Auto-Submit: Vadim Shtayura <vadimsh@chromium.org>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>