Apply kati output rewriting to dumpvars

This way we strip out ANSI codes when using dumb terminals. It's likely
overkill to use katiRewriteOutput, but we should rarely see any output
on stderr while dumping variables. This also lets us turn on kati_stats.

Bug: 71729611
Test: lunch missing-eng             (colored error)
Test: lunch missing-eng 2>&1 | cat  (non-colored)
Test: TERM=dumb lunch missing-eng   (non-colored)
Change-Id: Ic63fd42d82a4a64e5c68aecd9ae0f242a0d703f1