perf: do not hide model button when loading

[tisfeng]

https://github.com/tisfeng/Easydict/assets/25194972/9d09e48d-c5da-4c73-babd-c7aed26eafa0

[phlpsong]

Looks good, but I found some layout problems need to take a look:

1. Model text switched to some other model name when pointer hover on it

https://github.com/tisfeng/Easydict/assets/103433299/b1bb18cc-4628-482a-8516-0a1982102ecb

2. The warning image has an overlap issue with the model selection button

   

3. The loading icon is out of the bounds of the area and overlaps with the arrow image, it could be more obvious if service name is longer

https://github.com/tisfeng/Easydict/assets/103433299/e0d24ff0-f8c8-40a0-be05-0b877f6f4967

[tisfeng]

All the issues have been resolved.

I increased the minimum width of the window a bit, limited the length of custom OpenAI names, and also limited the maximum length of the service name label and model button.

[tisfeng]

Show service name label and model button width based on window width ratio, if window has enough width, they can be shown fully.

[phlpsong]

https://github.com/tisfeng/Easydict/assets/103433299/c5d9b56d-5587-493e-85c8-f9124b1cc581

This issue still exists if you press the modal name instead of hovering over it.

[tisfeng]

ok, fixed.

EZButton is a control I wrote casually at that time. This is my first time writing a macOS application, and many codes were not very good 😥

Although the code is bad, there is no need to optimize it. Let's rewrite it with SwiftUI later.