Migrate UI "ignore dependencies" does not force import

Problem/Motivation

When I execute a migration import in the Migrate UI and enable the "Ignore dependencies" checkbox, if the migration is missing dependencies, the import fails with the following error message in dblog:

Migration mymigrate_alias did not meet the requirements. Missing migrations mymigrate_announcement, mymigrate_basic_page, mymigrate_service. requirements: mymigrate_announcement. requirements: mymigrate_basic_page. requirements: mymigrate_service.

After the failure, I successfully ran the same migrate import from drush, using the following command:
drush migrate-import mymigrate_alias --force

Proposed resolution

The migration import with "Ignore dependencies" option in the UI should behave like the drush version of the operation with --force.

(It looks *to me,* when I look at the source code, like that's the intended behavior??)

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet