Rename dex2oat datum IDs

The new names make it clearer which ones are counters or histograms,
and what the units are for each one.

See also: https://r.android.com/1715490

Bug: 170149255
Test: m
Change-Id: I0917dbdeafe0b4496ca7df04bd9801d1b19e3dcb
2 files changed