Restore GraphQL schema merge for Relay query text

relay-compiler requires a single schema file: a directory is rejected
and schemaExtensions marks fields as client-only, so it emitted
text: null and the console posted query: null, getting a 400 on every
operation.

Restore the merge step (contrib/merge-graphql-schema.sh, the
RELAY_SCHEMAS make rules, and the gitignore entry) and point each
relay.config.json project back at the merged schema.graphql. The IDE
graphql-config removal and npm-script cleanup are unrelated and stay.

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

relay.config.json

@@ -10,8 +10,7 @@
   },
   "projects": {
     "core": {
-      "schema": "pkg/server/api/console/v1/graphql/base.graphql",
-      "schemaExtensions": ["pkg/server/api/console/v1/graphql"],
+      "schema": "pkg/server/api/console/v1/schema.graphql",
       "language": "typescript",
       "noFutureProofEnums": true,
       "output": "apps/console/src/__generated__/core",
@@ -26,8 +25,7 @@
       }
     },
     "iam": {
-      "schema": "pkg/server/api/connect/v1/graphql/base.graphql",
-      "schemaExtensions": ["pkg/server/api/connect/v1/graphql"],
+      "schema": "pkg/server/api/connect/v1/schema.graphql",
       "language": "typescript",
       "noFutureProofEnums": true,
       "output": "apps/console/src/__generated__/iam",
@@ -42,8 +40,7 @@
       }
     },
     "trust": {
-      "schema": "pkg/server/api/trust/v1/graphql/base.graphql",
-      "schemaExtensions": ["pkg/server/api/trust/v1/graphql"],
+      "schema": "pkg/server/api/trust/v1/schema.graphql",
       "language": "typescript",
       "noFutureProofEnums": true,
       "customScalarTypes": {