Cherry pick changes into our build

[setassociative]

This forks our 2019-04-02 build and "cherry picks" in the following changes:

1. Adds timeouts for all kinds of statements. Power to the clients! vitessio/vitess#4824 — Respect timeouts in all statements
2. properly suppress begin...commit in autocommit logs vitessio/vitess#4827 — Correctly suppress begin...commit in auto-commit logs
3. add optional tag-based filtering for query logging vitessio/vitess#4895 — Adds optional tag-based query logging
4. bootstrap.sh: Remove unused unused command. vitessio/vitess#4891 — fix build due to broken dependency

I squashed commits 2 and 3 each into a single commit on this branch. Item 2 did not apply cleanly so I had to manually resolve merge conflicts.

Once this merge is approved we will reset our master branch to point here and tag the old master branch so that it's not lost should we need to recover that state:

git checkout tinyspeck/master
git tag slack-vitess-2019.06.05
git reset --hard slack-vitess-2019.04.02.r1
git push -f tinyspeck

When it's time to sync back up with upstream we'll revert the 4 comments above and then merge vitessio/vitess master.

[rafael]

LGTM +1