Add `safeUriSchemes` setting (#20207)

This adds a `safeUriSchemes` global setting which lets you define
hyperlink URI schemes which the user considers safe. No confirmation
dialog will be shown when trying to open hyperlinks which use these
schemes.

- This solves the root issue, but doesn't introduce any UI or
  documentation changes. I wanted to validate the approach and
  implementation with you first.
- I closely followed the code handling the `disabledProfileSources`
  setting, which is of the same type.
- This feature does not change the behavior of `http`, `https` and
  `file` schemes.

Validation

I ran the dev terminal, and tested the behavior by clicking on `vscode`
hyperlinks generated by ripgrep with various `safeUriSchemes` settings:

- Setting not defined - asks for confirmation
- `["vscode"]` - does not ask for confirmation
- `["foo", "vscode"]` - does not ask for confirmation
- `["foo"]` - asks for confirmation
- `null` - asks for confirmation
- `[]` - asks for confirmation
- `[""]` - asks for confirmation
- `[{"foo": "bar"}]` - fails to deserialize (as expected)

A few uinit tests failed, but they seem unrelated to these changes:
- `KeyBindingTests` in `UnitTests_SettingsModel`, probably because I use
  an AZERTY keyboard.
- A few `Conhost` tests, but I didn't touch this part

Refs #20065
Closes #20191