Add replTest for :silent command

compiler/test-resources/repl/silent

@@ -0,0 +1,25 @@
+scala>:silent
+scala> 1+1
+scala> case class A(x: Int)
+scala> A("string")
+-- [E007] Type Mismatch Error: -------------------------------------------------
+1 | A("string")
+  |   ^^^^^^^^
+  |   Found:    ("string" : String)
+  |   Required: Int
+  |
+  | longer explanation available when compiling with `-explain`
+1 error found
+scala> Option[Int](2) match { case Some(x) => x }
+1 warning found
+-- [E029] Pattern Match Exhaustivity Warning: ----------------------------------
+1 | Option[Int](2) match { case Some(x) => x }
+  | ^^^^^^^^^^^^^^
+  | match may not be exhaustive.
+  |
+  | It would fail on pattern case: None
+  |
+  | longer explanation available when compiling with `-explain`
+scala>:silent
+scala> 1 + 2
+val res2: Int = 3