Add ability to display backgrounds for inlay hints

[maxdeviant]

This PR adds the ability to display backgrounds for inlay hints within the editor.

This is controlled by the new inlay_hints.show_background setting. This setting defaults to false.

To enable the setting, add the following to your settings.json:

{
  "inlay_hints": {
    "enabled": true,
    "show_background": true
  }
}

When enabled, the inlay hint backgrounds will use the hint.background color from the theme.

Disabled	Enabled

Related issues:

• Support text coloring and background coloring for inlay hints #12485
• hint/predictive theme stylings have no effect #17392

Release Notes:

• Added an inlay_hints.show_background setting to allow displaying backgrounds for inlay hints in the editor.
  • This setting defaults to false.
  • If enabled, the inlay hint backgrounds will use the hint.background color from the theme.

[AlbertMarashi]

would love to see this for predictive texts as well, because it helps me distinguish the generated code vs my actual code

[maxdeviant]

would love to see this for predictive texts as well, because it helps me distinguish the generated code vs my actual code

We can handle predictive text separately. I just wanted to focus on inlay hints, for now.

[AlbertMarashi]

@maxdeviant did you have an issue by any chance where inlay hint backgrounds were laid over the user selections, making the selection background invisible?

[HamzaFarhan]

@maxdeviant did you have an issue by any chance where inlay hint backgrounds were laid over the user selections, making the selection background invisible?

Yes. I kind of solved it using this but I would love a better solution:

"experimental.theme_overrides": {
    "predictive": "#FF0000"
}