Replace use of whitelist with allowlist and blacklist with denylist

In the spirit of our recent changes to Primary/Replica naming, we should also change other terminology in our ecosystem. One that immediately comes to mind in SkySQL is the "Whitelist". I suggest this is changed to "allowlist" and any references to "blacklist", instead be "denylist"

This is something other companies have done already, so it isn't a totally wild suggestion:

https://github.com/rails/rails/issues/33677
https://github.com/php/php-src/pull/5685