Bruno Leroux 1a8e57f42e
Use decoration hint text as the default value for dropdown button hints (#152474)
## Description

This PR makes `DropdownButtonFormField` hint defaults to the provided inputDecoration hintText.

Because `DropDownButtonFormField` accepts both a `hint` parameter and a `decoration`parameter, one can expect `InputDecoration.hintText` to be valid.

Before this PR, when `InputDecoration.hintText` was specified, it is shown but the vertical position is wrong.
After this PR, when `InputDecoration.hintText` is specified, it is used as the default value for `DropDownButtonFormField.hint` and `DropDownButtonFormField.disabledHint`.

| Before | After |
|--------|--------|
| ![image](https://github.com/user-attachments/assets/a08ff75c-edd4-4e16-9cfa-98ddb349d860) | ![image](https://github.com/user-attachments/assets/55f08bee-8f88-4125-8fae-68e2be724955) |

## Related Issue

Fixes https://github.com/flutter/flutter/issues/111958.

## Tests

Adds 5 tests.
2024-07-31 11:22:26 +00:00
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