Add functionality to make TextInput disabled

[JungleTryne]

People have been asking to add disabled state for several widgets in #1066. The most liked comment was about adding the state to the TextEdit widget. Indeed, it's quite useful to have functionalty to prevent user from changing the content of the text edit fields.

I added new logic and a theme for the widget to implement the functionality.

Now text edit can be enabled/disabled like this:

text_input(
  "Write something here",
  &self.data,
  Message::TextInputChanged,
).disabled(true);

[13r0ck]

I would rather this be like the button. Have the text input by default be disabled like a button, but have an on_change(MESSAGE) method.

[JungleTryne]

I would rather this be like the button. Have the text input by default be disabled like a button, but have an on_change(MESSAGE) method.

But that requires changing the API, which might break back-compatibility. It's not a problem to rewrite it, but I would like to know if it is okay to actually implement breaking changes at this point

[JungleTryne]

I changed API, now it works like a button. It is not enabled if there is no callback for on_change.

I also change the example, I added an async 3 seconds timer to test an edge-case when the field is focused and gets disabled, suggested in discord by nicoburns#9458.

Finally, I updated all examples for the new API

[hecrj]

Thank your taking a shot at this! 🙇

I have made some important changes:

• Renamed on_change to on_input in e6a93e9. I believe it conveys more intent.
• Added some diffing logic to unfocus the input if it suddenly becomes disabled in 7e69cb4.
• Fine-tuned the disabled styling a bit in 1de794a.
• Changed the mouse_interaction to display a new NotAllowed mouse icon when hovering a disabled input in 7e7e665.

And that's it! Let's merge!