test(psl): add missing test cases for multiple generators with the same provider name (#5505)

This PR adds missing test cases for multiple generators with the same
provider name

Co-authored-by: jkomyno <12381818+jkomyno@users.noreply.github.com>

Author: jkomyno

psl/psl/tests/validation/generator/multiple_prisma_clients.prisma

@@ -0,0 +1,18 @@
+generator client {
+  provider = "prisma-client"
+  output = "../lib/.generated/prisma"
+  previewFeatures = ["driverAdapters", "queryCompiler"]
+}
+
+generator edge {
+  provider = "prisma-client"
+  output = "../lib/.generated/prisma-edge"
+  runtime = "edge-light"
+  previewFeatures = ["driverAdapters", "queryCompiler"]
+}
+
+datasource db {
+  provider  = "postgresql"
+  url       = env("DATABASE_URL")
+  directUrl = env("DIRECT_URL")
+}

psl/psl/tests/validation/generator/multiple_prisma_clients_same_name.prisma

@@ -0,0 +1,23 @@
+generator client {
+  provider = "prisma-client"
+  output = "../lib/.generated/prisma"
+  previewFeatures = ["driverAdapters", "queryCompiler"]
+}
+
+generator client {
+  provider = "prisma-client"
+  output = "../lib/.generated/prisma-edge"
+  runtime = "edge-light"
+}
+
+datasource db {
+  provider  = "postgresql"
+  url       = env("DATABASE_URL")
+  directUrl = env("DIRECT_URL")
+}
+// error: The generator "client" cannot be defined because a generator with that name already exists.
+//   -->  schema.prisma:7
+//    | 
+//  6 | 
+//  7 | generator client {
+//    |