Also hexencode non-utf8 binaries. This is essentially an heuristic.
We don't know column types in runtime, and there's no simple way
to find them out. Since we're already doing full binary scan during
escaping it should be cheap to bail out on non-utf8 strings and
hexencode them instead.
Also introduce separate function to highlight that this escaping
is MySQL-specific.
Due to:
* Cluster RPC MFA is not idempotent!
* There is a lack of rollback for callback's side-effects
For instance, when two nodes try to add a cluster-singleton
concurrently, one of them will have to wait for the table lock
then try to catch-up, then try to apply MFA.
The catch-up will have the singleton created, but the initiated
initiated multicall apply will fail causing the commit to rollback,
but not to 'undo' the singleton creation.
Later, the retries will fail indefinitely.
