Statsd: Remove storage of bucketNum

Past buckets had a field mBucketNum, storing the
"bucket number" they represented. Currently, the concept
of bucket number is used by Anomaly Detection (although this
may not be necessary), but these stored values are not used at all,
so removing them will save RAM.

Test: statsd tests still pass
Bug: 74607818
Change-Id: Iacc343bc39c5035f6e2f236c03de1d91606eff4c
10 files changed