Fixes BankFrom.*Timings

[brooksprumo]

Problem

The BankFromArchive/DirTimings, and everything touching it, irks me. The names a sometimes unnecessarily verbose, or terse; sometimes grammatically inconsistent; sometimes strangely ordered; sometimes poorly documented. Since I look at this code somewhat often, I'd like it to be nicer.

Summary of Changes

• BankFromArchiveTimings -> BankFromArchivesTimings
• reorder and standardize fields
• rename metrics
• remove unused/duplicate BankFrom.*Timings that were also in runtime/src/snapshot_utils.rs
• rename rebuild_storages_from_snapshot_dir(), and fixup the documentation

[brooksprumo]

@apfitzge - requested your review since you've reviewed this code previously (and all the fastboot stuff in general)
@steviez - requested your review since you're the only other person that might look at these metrics

[codecov]

Codecov Report

Merging #34249 (8e17b1b) into master (b741c9c) will increase coverage by 0.0%.
Report is 4 commits behind head on master.
The diff coverage is 60.0%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #34249   +/-   ##
=======================================
  Coverage    81.9%    81.9%           
=======================================
  Files         819      819           
  Lines      219387   219369   -18     
=======================================
+ Hits       179690   179742   +52     
+ Misses      39697    39627   -70     

[apfitzge]

lgtm. New names seem better to me.

[steviez]

I'm all for it!