[CLI]: Verb/Option for configuring "behavioral" feature flags (`--enable-feature-123`)

To track as a separate issue, I think we should add a different `dab` command that helps to enable or disable a feature, should not be only possible through the `init` command - which is the case today.

_Originally posted by @Aniruddh25 in https://github.com/Azure/data-api-builder/pull/1983#discussion_r1468255119_

Create a new command to create/update feature flags in the config file.