[17.06] Add metrics for store object types

[dperny]

Adds metrics for most of the user-facing store object types. Allows the
user to keep track of how many objects are in the object store at any
given time.

Cherry picks #2673, applies cleanly

(cherry picked from commit b67abf8)

[codecov]

Codecov Report

Merging #2679 into bump_v17.06 will decrease coverage by 0.48%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           bump_v17.06    #2679      +/-   ##
===============================================
- Coverage        61.66%   61.18%   -0.49%     
===============================================
  Files               42      121      +79     
  Lines             5692    20172   +14480     
===============================================
+ Hits              3510    12342    +8832     
- Misses            1841     6472    +4631     
- Partials           341     1358    +1017