feat: move compat database to separate package (#4436)

* feat: move compat database to separate package

The packageExtensions compat database is useful for pnpm as well.
By moving it to a separate package, we can use it in pnpm and
recommend the pnpm users to extend the database as well.

* Renames packages/extensions -> packages/yarnpkg-extensions

* Fixes constraints

* refactor: re-use extensions

* chore: remove unnecessary test

* chore: start at `1.0.0`

Co-authored-by: Maël Nison <nison.mael@gmail.com>
Co-authored-by: merceyz <merceyz@users.noreply.github.com>

.yarn/versions/1633b796.yml

@@ -0,0 +1,5 @@
+releases:
+  "@yarnpkg/extensions": minor
+
+declined:
+  - "@yarnpkg/plugin-compat"

packages/gatsby/static/configuration/yarnrc.json

@@ -529,7 +529,7 @@
     },
     "packageExtensions": {
       "_package": "@yarnpkg/core",
-      "description": "Some packages may have been specified incorrectly with regard to their dependencies - for example with one dependency being missing, causing Yarn to refuse it the access. The `packageExtensions` fields offer a way to extend the existing package definitions with additional information. If you use it, consider sending a PR upstream and contributing your extension to the [`plugin-compat` database](https://github.com/yarnpkg/berry/blob/master/packages/plugin-compat/sources/extensions.ts).\nNote: This field is made to add dependencies; if you need to rewrite existing ones, prefer the [`resolutions`](/configuration/manifest#resolutions) field.",
+      "description": "Some packages may have been specified incorrectly with regard to their dependencies - for example with one dependency being missing, causing Yarn to refuse it the access. The `packageExtensions` fields offer a way to extend the existing package definitions with additional information. If you use it, consider sending a PR upstream and contributing your extension to the [`plugin-compat` database](https://github.com/yarnpkg/berry/blob/master/packages/extensions/sources/index.ts).\nNote: This field is made to add dependencies; if you need to rewrite existing ones, prefer the [`resolutions`](/configuration/manifest#resolutions) field.",
       "type": "object",
       "patternProperties": {
         "^(?:@([^/]+?)/)?([^/]+?)(?:@(.+))$": {

packages/plugin-compat/package.json

@@ -7,6 +7,9 @@
     "@yarnpkg/core": "workspace:^",
     "@yarnpkg/plugin-patch": "workspace:^"
   },
+  "dependencies": {
+    "@yarnpkg/extensions": "workspace:^"
+  },
   "devDependencies": {
     "@types/lodash-es": "4.17.4",
     "@types/resolve": "^1.17.1",