Migrated the documentations and test cases in the Persistence package to use/name PostgreSQL instead.

Packages/Persistence/Tests/Cases/Public/Methods/ProbeTests.swift

@@ -19,7 +19,7 @@ struct ProbeTests {
             driver: .inMemory,
             logger: Logger(label: "test")
         )
-        let fluent = service()
+        let fluent = try service()
         let probe = Probe(fluent: fluent)
 
         let isReachable = await probe()
@@ -34,7 +34,7 @@ struct ProbeTests {
         // Port 1 on the loopback interface has nothing listening, so the connection is refused
         // immediately instead of timing out.
         let service = Service(
-            driver: .mysql(
+            driver: .postgres(
                 .init(
                     host: "127.0.0.1",
                     port: 1,
@@ -47,7 +47,7 @@ struct ProbeTests {
             ),
             logger: Logger(label: "test")
         )
-        let fluent = service()
+        let fluent = try service()
         let probe = Probe(fluent: fluent)
 
         let isReachable = await probe()