tools: add project option to log_since.py
tools: add project option to log_since.py

This is replacement for cl/297813124

Change-Id: I82e5d092bf8a8a4f7975f277794bf7bbc7694346
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2086511
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py