Upgrade Relay to v20.1.1 and unify compiler config

Consolidate the two per-app relay configs (console and trust)
into a single multi-project relay.config.json at the repo root
with three projects: core, iam, and trust. Bump all relay
packages from v19 to v20.1.1 and move relay-compiler to the
root devDependencies. Replace per-workspace relay scripts with
a single root-level npm run relay command and update the
GNUmakefile, CI workflows, and docs accordingly.

Signed-off-by: Émile Ré <emile@getprobo.com>

package.json

@@ -14,9 +14,12 @@
     "dev": "turbo run dev",
     "lint": "turbo run lint",
     "check": "turbo run check",
-    "relay": "turbo run relay"
+    "relay-clean": "find apps -type d -name __generated__ -exec rm -rf {} +",
+    "relay-compile": "npx relay-compiler",
+    "relay": "npm run relay-clean && npm run relay-compile"
   },
   "devDependencies": {
+    "relay-compiler": "^20.1.1",
     "turbo": "^2.5.3"
   },
   "graphql": {