Easily enable automatic Dolt commits via `@@dolt_transaction_commit`

[fulghum]

A customer is working on integrating Hosted Dolt into some of their existing systems. Some of these systems want to directly use Dolt's versioning features, but many others just want to interact with Hosted Dolt as if it were a normal MySQL database. The customer would like those interactions to still create Dolt commits. They were unaware of the @@dolt_transaction_commit setting that automatically creates Dolt commits from SQL commits and thought this would be an excellent fit for them. Since this feature is so useful for them, and likely for other customers who don't know about it yet, they asked us to consider making it more prominent in the UI.

One suggestion was to expose @@dolt_transaction_commit from a Hosted Dolt Deployment configuration section, just like we do for @@autocommit. (It would be nice to have a short snippet of description for each configuration item, btw, or at least a link to more documentation.)

It might also be interesting to consider showing it to customer upfront during the deployment creation, but I don't want to make the launch wizard more complex than it needs to be.

[tbantle22]

I added help popups with config item descriptions

[tbantle22]

This is now available when you upgrade the Dolt version of your instance to 1.2.0