[IR] Dump IdSignatures and mangled names in irText tests

The reason #1 for this feature is that we want to test IdSignatures
generated for declarations. Currently, there is no (easy) way to ensure
that a change in the signature building logic doesn't cause any breaking
changes wrt klibs.

Now, most IdSignatures include hashed mangled names in them, so even if
we catch a regression where the included hash changes, there would be no
way of knowing immediately what caused it, unless we'd also have mangled
names in the expectations.

The reason #2 is to test the manglers themselves. Currently, there are
no tests for them. They heavily duplicate each other, this is already
causing issues (see KT-57427) that would be very hard to catch without
these tests.

^KT-58238 Fixed

compiler/testData/ir/irText/expressions/funInterface/arrayAsVarargAfterSamArgument_fi.sig.kt.txt

@@ -0,0 +1,27 @@
+// CHECK:
+//   Mangled name: IRunnable
+//   Public signature: /IRunnable|null[0]
+fun interface IRunnable {
+
+  // CHECK:
+  //   Mangled name: IRunnable#run(){}
+  //   Public signature: /IRunnable.run|-991178076551934874[0]
+  abstract fun run(): Unit
+
+}
+
+// CHECK:
+//   Mangled name: #foo1(IRunnable;kotlin.Array<out|kotlin.String>...){}
+//   Public signature: /foo1|8109256075034655920[0]
+fun foo1(r: IRunnable, vararg s: String): Unit
+
+// CHECK:
+//   Mangled name: #foo2(IRunnable;IRunnable;kotlin.Array<out|kotlin.String>...){}
+//   Public signature: /foo2|-847052428556006975[0]
+fun foo2(r1: IRunnable, r2: IRunnable, vararg s: String): Unit
+
+// CHECK:
+//   Mangled name: #test(kotlin.Function0<kotlin.Unit>;IRunnable;kotlin.String;kotlin.Array<kotlin.String>){}
+//   Public signature: /test|8261026842322841823[0]
+fun test(fn: Function0<Unit>, r: IRunnable, s: String, arr: Array<String>): Unit
+