Chinese font width error when using third party font

Hi,
When I change default font to some third party font
such as
`editor.font=Source Code Pro,plain,13`
and
`editor.font=JetBrains Mono,plain,13`
in `preferences.txt`, Chinese font width(2 English character width) narrowed, but display as expected.
When selecting Chinese text, the highlight width is only one English character width.

```
Arduino IDE version: 1.8.13 (also tested in the nighty version)
Operating system: Archlinux
```

Reproduce the issue in Arduino IDE 1.8.13 on Arch Linux using preferences.txt with Source Code Pro and JetBrains Mono. Start by tracing the editor's font measurement and text-selection highlighting behavior; done means Chinese selection highlights span the displayed two-character width with third-party fonts.

Written by the indexing model from the issue text.