Deprecate code actions on format setting

[probably-neb]

Closes #ISSUE

Release Notes:

• settings: Deprecated code_actions_on_format in favor of specifying code actions to run on format inline in the formatter array.

Previously, you would configure code actions to run on format like this:

{
  "code_actions_on_format": {
    "source.organizeImports": true,
    "source.fixAll.eslint": true
  }
}

This has been migrated to the new format:

{
  "formatter": [
    {
      "code_action": "source.organizeImports"
    },
    {
      "code_action": "source.fixAll.eslint"
    }
  ]
}

This change will be automatically migrated for you. If you had an existing formatter setting, the code actions are prepended to your formatter array (matching the existing behavior). This migration applies to both global settings and language-specific settings