[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/stringPlus.sig.kt.txt

@@ -0,0 +1,24 @@
+// CHECK JVM_IR:
+//   Mangled name: #test1(kotlin.String;kotlin.Any){}kotlin.String
+//   Public signature: /test1|2440544200321987910[0]
+// CHECK JS_IR NATIVE:
+//   Mangled name: #test1(kotlin.String;kotlin.Any){}
+//   Public signature: /test1|-8076416945130465068[0]
+fun test1(a: String, b: Any): String
+
+// CHECK JVM_IR:
+//   Mangled name: #test2(kotlin.String;kotlin.Int){}kotlin.String
+//   Public signature: /test2|9065897195329223931[0]
+// CHECK JS_IR NATIVE:
+//   Mangled name: #test2(kotlin.String;kotlin.Int){}
+//   Public signature: /test2|6075955926134197604[0]
+fun test2(a: String, b: Int): String
+
+// CHECK JVM_IR:
+//   Mangled name: #test3(kotlin.String;kotlin.Int){}kotlin.String
+//   Public signature: /test3|3363196109253524910[0]
+// CHECK JS_IR NATIVE:
+//   Mangled name: #test3(kotlin.String;kotlin.Int){}
+//   Public signature: /test3|-788223786464412990[0]
+fun test3(a: String, b: Int): String
+