Search bar for Settings UI

[vadimkantorov]

When there's many global settings, it's useful to have a search bar (Windows Settings and other complex software packages feature this).

Another feature may auto-save for Settings. Windows Settings has this (more debatable).

### Tasks

[vadimkantorov]

• maybe a separate search/filter bar would be helpful for keybindings window

[zadjii-msft]

• maybe a separate search/filter bar would be helpful for keybindings window

see #11630

[g0t4]

I prefer to chose when to Save settings changes, please don't automatically do that!

[g0t4]

💯 Settings search would be useful given the plethora of (well organized) tabs and nested configuration.

Use cases:

• Finding where a setting is located
• Discovering new settings
• Linking to related, external settings (i.e. Cursor blink rate is in Keyboard Properties Windows control panel)

Ideas:

• The settings schema has stellar descriptions/enums/etc so that could be an easy way to bootstrap search data:
  • i.e. https://raw.githubusercontent.com/microsoft/terminal/release-1.19/doc/cascadia/profiles.schema.json
  • I use this as a workaround to discover settings.