Dramatically speed up npm/yarn completions

These go from a minimum of 5s in release mode to instantaneous. Worst case was
more than 30s when we didn't find enough matches to end early.

share/functions/__fish_npm_helper.fish

@@ -32,8 +32,15 @@ function __npm_filtered_list_packages
     # Do not provide any completions if nothing has been entered yet to avoid long hang.
     if string match -rq . (commandline -ct)
         # Filter the results here rather than in the C++ code due to #5267
-        all-the-package-names | string match -er -- '(?:\b|_|^)'(commandline -ct |
-            string escape --style=regex) | head -n1000
+        # `all-the-package-names` reads a billion line JSON file using node (slow) then prints
+        # it all (slow) using node (slow). Directly parse the `names.json` file that ships with it instead.
+        for path in {$HOME/.config/yarn/global,$HOME/.npm-global/lib,/usr/local/lib}/node_modules/all-the-package-names/names.json
+            test -f $path || continue
+            # Using `string replace` directly is slow because it doesn't know to stop looking after a match cannot be
+            # found in the alphabetically sorted list. Use `look` for its binary search support.
+            look '  "'(commandline -ct) $path | string replace -rf '^  "(.*?)".*' '$1'
+            break
+        end
     end
 end