Report to New Relic certain per-request details about the
DjangoXBlockUserStateClient.  The following metrics are reported for the
get_many() call:

xb_user_state.get_many.calls
xb_user_state.get_many.duration
xb_user_state.get_many.blocks_requested
xb_user_state.get_many.blocks_out
xb_user_state.get_many.size
xb_user_state.get_many.<block_type>.blocks_requested
xb_user_state.get_many.<block_type>.blocks_out
xb_user_state.get_many.<block_type>.size

Similarly, for the set_many() call:

xb_user_state.set_many.calls
xb_user_state.set_many.duration
xb_user_state.set_many.blocks_created
xb_user_state.set_many.blocks_updated
xb_user_state.set_many.size
xb_user_state.set_many.<block_type>.blocks_created
xb_user_state.set_many.<block_type>.blocks_updated
xb_user_state.set_many.<block_type>.size

Where <block_type> is one of "chapter", "course", "problem", "video",
etc.

PERF-354