Fix: restore searchable dropdown for DAG params enum fields

[nagasrisai]

The DAG params dropdown was searchable in Airflow 2. You could type to narrow the list down to the option you wanted. That stopped working in Airflow 3.

Switched FieldDropdown to use chakra-react-select which already provides built-in search, consistent with how FieldMultiSelect works in the same directory. Removed the custom Input workaround and the unused translation key that came with it.

Closes #63879

[nagasrisai]

Let me know if anything needs adjusting.

[bbovenzi]

We use chakra-react-select elsewhere in the UI if we want to allow searching

[nagasrisai]

Done, switched to chakra-react-select. Also removed the custom search input and the translation key that are no longer needed.
@bbovenzi could you please review ?

[bbovenzi]

Can you provide a video or gif of the functionality?

[nagasrisai]

Here are some screenshots from running the fix locally on a DAG with 12 enum params.

Clicking the field opens the full list:

Typing filters it down in real time — here searching "east" narrows it to the matching regions:

All 12 params render as searchable dropdowns. String, integer, and other param types are unaffected since the change only applies when param.schema?.enum is present.

[nagasrisai]

Here's a gif showing the full interaction — dialog opening, full list rendering, then searching live as you type:

The first frame shows the dropdown closed with the current value. Clicking opens the full option list. Typing narrows it down in real time.

[pierrejeambrun]

Working as expected, looking good to me.

We just need to remove the screenshots.