Trace SQLite operations

Inefficient SQLite use can have non-obvious effects on performance.  For
example, insert and update operations can trigger a surprising number of
fsync() calls, especially if they're not grouped together into
transactions.

Add tracepoints around SQLite operations, to make it easier to pinpoint
their effects on the rest of the system.

Change-Id: I30cc3d02eca264e46dcc09ca7512a32519543834
Signed-off-by: Greg Hackmann <ghackmann@google.com>