Japanese IMEs do not work in the "open file in project" widget (Windows)

Describe the bug
The text entry field in the "open file in project" widget does not seem to support entry via Google Japanese IME or Microsoft IME. I only use it for Japanese but I imagine it might affect other languages that work similarly.

I tried modifying the source code for filteredit.cpp to setAttribute(Qt::WA_InputMethodEnabled) in the constructor after doing some googling but that wasn't enough to fix this.

Not sure if this is platform specific but had @eishiya and myself confirm on Windows.

To Reproduce
Steps to reproduce the behavior:

1. Install Google IME or Microsoft IME Japanese input.
2. Go to 'Open Files in Project'
3. Switch to Japanese input
4. Attempt to enter text in Japanese
5. Observe that text cannot be entered

Expected behavior
This field should allow text to be entered in Japanese.

Media
When the "open file in project" widget is focused, google IME reports being disabled

IME working in another text field in Tiled

Note:
We might want to test out some of the widgets in the new Dialog functionality and see if any of them suffer the same problem, and if so apply the solution there too.

Specifications:

• OS: Windows 10
• Tiled Version: 1.9.0