Rename to_dict to populate in FormDefintion to fix bug

[jdavcs]

Old method was overriding the method defined in a mixin (with a different signature) that was called from api.forms

For context, see discussion on backend channel:
The model.FormDefinition.to_dict() method (added in 09/2016 in #3118) takes user, value, and security arguments, which overrides the to_dict definition in the Dictifiable mixin, which takes view and value_mapper as arguments. So, if we call the to_dict method on a FormDefinition object passing it the view/value_mapper arguments, an error will be raised. However, we have (at least) 4 places where we call this method on this object: in galaxy.api.forms it's called in the index, show and create methods with the WRONG arguments (view, value_mapper), and in galaxy.api.users with the CORRECT arguments (user, values, security), which is the ONLY place in lib where it's called with those arguments.

Bug discovered via mypy after adding type annotations in #16434.

How to test the changes?

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• 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

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[jdavcs]

test failures unrelated