migrate to pnpm (#609)

* migrate to `pnpm`

* rename `simple-project` fixture packages to remove socket security errors

* add pnpm `dedupe` options

* update release-pr workflow

* update

* update snashots

* tweaks

* tweak

* tweak

* fix missing ci-setup

* tweak

* tweak deps

* update pnpm

* ok, Socket, let's rename them

* update snapshots

* rename again

* fmt

---------

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

__fixtures__/simple-project/packages/pkg-a/package.json

@@ -1,7 +1,7 @@
 {
-  "name": "simple-project-pkg-a",
+  "name": "changesets-dev-simple-project-pkg-a",
   "version": "1.0.0",
   "dependencies": {
-    "simple-project-pkg-b": "1.0.0"
+    "changesets-dev-simple-project-pkg-b": "1.0.0"
   }
 }

__fixtures__/simple-project/packages/pkg-b/package.json

@@ -1,4 +1,4 @@
 {
-  "name": "simple-project-pkg-b",
+  "name": "changesets-dev-simple-project-pkg-b",
   "version": "1.0.0"
 }