There’s no way to trigger a test against an MR if the project doesn’t have issue testing set by default

Problem/Motivation

There’s no way to trigger a test against an MR if the project doesn’t have issue testing set by default. See for example:

• https://www.drupal.org/project/field_group/issues/3244858 →
• https://www.drupal.org/project/commerce_elavon/issues/3245141 →

In the second example it wasn't possible to test against the correct version with the patch either.

See also https://drupal.slack.com/archives/C51GNJG91/p1634732599270600

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes