Assert that data_column parameters have a valid data_ref

[bernt-matthias]

• data_ref needs to be specified in the XML
• data_ref needs to refer to an existing parameter

Fixes #18359 (i.e. the misleading error message, since now the KeyError caused by missing/wrong data_ref are replaced by AssertionErrors which will be reported properly, but still as tool loading error)

Questions:

• Do we need a profile version for this?
• I could add linter rule(s) for this, but I guess this should be done in a larger project analogous to this, which should cover all allowed/required attribute combinations for <param>?

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

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