firmware_TouchMTB: add metrics for linearity validator

BUG=chromium:248120
TEST=Replay logs on a lumpy.
$ cd /usr/local/autotest/tests/firmware_TouchMTB
$ tools/machine_replay.sh -b tests/logs/lumpy/ -s
And then run the summary script to generate a summary report.
$ ./summary.sh -d /tmp -m
Observe the metrics for linearity are show like

fw_11.27: {
  'max_err_x_mm': (2.6546, 2.6546, 2.6546),
  'max_err_y_mm': (0.3314, 0.3314, 0.3314),
  'rms_err_x_mm': (1.3401, 1.3401, 1.3401),
  'rms_err_y_mm': (0.2162, 0.2162, 0.2162),
}

Change-Id: I081b84d2671e23126c4def1c1b517417ffe0909c
Reviewed-on: https://gerrit.chromium.org/gerrit/58085
Reviewed-by: Charlie Mooney <charliemooney@chromium.org>
Tested-by: Joseph Shyh-In Hwang <josephsih@chromium.org>
Commit-Queue: Joseph Shyh-In Hwang <josephsih@chromium.org>
9 files changed