Allow directory_uri workflow parameters.

[jmchilton]

Implements #13184 as requested by @Delphine-L for the VGP workflows.

How to test the changes?

(Select all options that apply)

• Instructions for manual testing are as follows:
  1. Create a workflow with a new directory URI input and connect it to a directory_uri input. If you run Galaxy with GALAXY_RUN_WITH_TEST_TOOLS=1, then gx_directory_uri will be available. You will need to mark that input as connectable so the input appears in the editor.
  2. Click run the workflow - pick an output directory and run the workflow.
  3. See everything turn green.

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[mvdbeek]

Thanks @jmchilton!