Add allow_rewrap setting to control editor::Rewrap behavior for a given language (#25173)

This PR adds a new `allow_rewrap` setting to control how
`editor::Rewrap` behaves for a given language.

This is a language setting, so it can either be configured globally or
within the context of an individual language.

For example:

```json
{
  "allow_rewrap": "in_selections",
  "languages": {
    "Typst": {
      "allow_rewrap": "anywhere"
    }
  }
}
```

There are three different values:

- `in_comment`: Only perform rewrapping within comments.
- `in_selections`: Only perform rewrapping within the current
selection(s).
- `anywhere`: Allow rewrapping anywhere.

The global default is `in_comment`, as it is the most conservative
option and allows rewrapping comments without risking breaking other
syntax.

The `Markdown` and `Plain Text` languages default to `anywhere`, which
mirrors the previous behavior for those language that was hard-coded
into the rewrap implementation.

This setting does not have any effect in Vim mode, as Vim mode already
allowed rewrapping anywhere.

Closes https://github.com/zed-industries/zed/issues/24242.

Release Notes:

- Added an `allow_rewrap` setting to control the `editor::Rewrap`
behavior for a given language.

assets/settings/default.json

@@ -204,6 +204,23 @@
   // Otherwise(when `true`), the closing characters are always skipped over and auto-removed
   // no matter how they were inserted.
   "always_treat_brackets_as_autoclosed": false,
+  // Controls where the `editor::Rewrap` action is allowed in the current language scope.
+  //
+  // This setting can take three values:
+  //
+  // 1. Only allow rewrapping in comments:
+  //    "in_comments"
+  // 2. Only allow rewrapping in the current selection(s):
+  //    "in_selections"
+  // 3. Allow rewrapping anywhere:
+  //    "anywhere"
+  //
+  // When using values other than `in_comments`, it is possible for the rewrapping to produce code
+  // that is syntactically invalid. Keep this in mind when selecting which behavior you would like
+  // to use.
+  //
+  // Note: This setting has no effect in Vim mode, as rewrap is already allowed everywhere.
+  "allow_rewrap": "in_comments",
   // Controls whether edit predictions are shown immediately (true)
   // or manually by triggering `editor::ShowEditPrediction` (false).
   "show_edit_predictions": true,
@@ -1103,6 +1120,7 @@
     "Markdown": {
       "format_on_save": "off",
       "use_on_type_format": false,
+      "allow_rewrap": "anywhere",
       "prettier": {
         "allowed": true
       }
@@ -1115,6 +1133,9 @@
         "parser": "php"
       }
     },
+    "Plain Text": {
+      "allow_rewrap": "anywhere"
+    },
     "Ruby": {
       "language_servers": ["solargraph", "!ruby-lsp", "!rubocop", "..."]
     },