Add Configuration for Default Cascade Option for Foreign Keys

[mercury-kuba]

Context

We want to be able to set the default cascade option when running migrations. Currently, the default cascade option is fixed to Restrict, and we maintain that default in emptyBackendSpecificOverrides, but allow for customization.

For our specific use case, we'd like to default to NoAction instead of Restrict.

Default Template

Before submitting your PR, check that you've:

• Documented new APIs with Haddock markup
• Added @since declarations to the Haddock
• Ran fourmolu on any changed files (restyled will do this for you, so
  accept the suggested changes if it makes them)
• Adhered to the code style (see the .editorconfig and fourmolu.yaml files for details)

After submitting your PR:

• Update the Changelog.md file with a link to your PR
• Bumped the version number if there isn't an (unreleased) on the Changelog
• Check that CI passes (or if it fails, for reasons unrelated to your change, like CI timeouts)