Un-mark workflow deletion

Description

Currently, marking a workflow for deletion by clicking the delete button updates the deleted_at column in the database and disables all jobs for that workflow. This action results in the project page only showing workflows that do not have a deleted_at timestamp.

However, this process poses two challenges for users:

• Users cannot create a new workflow with the same name as the one marked for deletion.
• Users do not have the ability to un-mark the workflow deletion once it has been initiated.

Steps to Reproduce

• Click the delete button on a workflow.
• Attempt to create a new workflow with the same name.
• Attempt to un-mark the workflow deletion.

Expected Behavior.

1. Users should be able to create a new workflow with the same name as the one marked for deletion.
2. Users should have the ability to un-mark the workflow deletion if needed.

Additional context

See Mark workflow deletion PR

Start by reading the linked Mark workflow deletion PR (#605) and trace the workflow deletion flow described in this issue. Done means a deleted workflow can be un-marked and a new workflow can reuse its name, while the existing deletion behavior remains consistent.