Auto-convert filter input to string if necessary

Coming from #2654892: Allow using data filters in placeholder tokens:

The 'default' filter can currently only filter on strings, so node:title is not a valid input while node:title:value would be. As we can convert everything to strings via $typed_data->getString() we should probably implement some logic that invokes that function for filters that need string input.

Thus, we need to check whether the next filter input accepts the data of the current type, if not try it again with a string. If that works, auto-convert it via getString().