[Draft] Create/edit run configuration

[craig-willis]

Revised based on 6/14/21 dev call

Requirements:

• A tale has a single default run configuration (see [Draft] New endpoints to manage recorded run configurations girder_wholetale#492)
• The user can edit the run configuration (i.e., the entrypoint script, test script)
• A tale can have multiple run configurations
• The user can add, edit, rename, configurations The
• A run configuration consists of a name, the path to an entrypoint script (required) and test script (optional). (Note: "type" in the mockups will not be supported and can be ignored).

Mockups:
Mockups for this feature are incomplete. There is one from @hategan's proof-of-concept and another partial mockup.

• Versioning / Recorded Run UI presentation slide 6.
• Recorded Run Mockup -- Edit configuration UI is not defined.

[hategan]

• Note: "type" in the mockups will not be supported and can be ignored.

Maybe this is referring to an initial iteration, but, in my opinion, supporting at least local and container are important to allow a decent development workflow. The idea being that "local" allows uses to quickly invoke an executable for testing purposes and rapid prototyping, but provides little guarantees of reproducibility, whereas "container" involves building a container from scratch, which is not suitable for rapid prototyping since it tends to take a long time, but essential for reproducibility.