Make word completions less intrusive (#36745)

Introduce `min_words_query_len` threshold for automatic word completion
display, and set it to 3 by default.

Re-enable word completions in Markdown and Plaintext.

Release Notes:

- Introduced `min_words_query_len` threshold for automatic word
completion display, and set it to 3 by default to make them less
intrusive

assets/settings/default.json

@@ -1503,6 +1503,11 @@
     //
     // Default: fallback
     "words": "fallback",
+    // Minimum number of characters required to automatically trigger word-based completions.
+    // Before that value, it's still possible to trigger the words-based completion manually with the corresponding editor command.
+    //
+    // Default: 3
+    "words_min_length": 3,
     // Whether to fetch LSP completions or not.
     //
     // Default: true
@@ -1642,9 +1647,6 @@
       "use_on_type_format": false,
       "allow_rewrap": "anywhere",
       "soft_wrap": "editor_width",
-      "completions": {
-        "words": "disabled"
-      },
       "prettier": {
         "allowed": true
       }
@@ -1658,9 +1660,6 @@
       }
     },
     "Plain Text": {
-      "completions": {
-        "words": "disabled"
-      },
       "allow_rewrap": "anywhere"
     },
     "Python": {