Add configurable edge distance for latency test

BUG=b:241909914
TEST=None

Change-Id: I6909064eaf084069227ca75802bb3d939f4b2836
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/optofidelity_TPPT/+/7075335
Tested-by: Sean O'Brien <seobrien@chromium.org>
Reviewed-by: Kenneth Albanowski <kenalba@google.com>
Reviewed-by: Jingyuan Liang <jingyliang@chromium.org>
Commit-Queue: Sean O'Brien <seobrien@chromium.org>