[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/declarations/defaultArguments.sig.kt.txt

@@ -0,0 +1,8 @@
+// CHECK:
+//   Mangled name: #test1(kotlin.Int;kotlin.Int;kotlin.String){}
+//   Public signature: /test1|-2420205866450198550[0]
+fun test1(x: Int, y: Int, z: String): Unit
+  // CHECK:
+  //   Mangled name: #test1(kotlin.Int;kotlin.Int;kotlin.String){}#local#static(kotlin.Int;kotlin.Int;kotlin.String){}
+  local fun local(xx: Int, yy: Int, zz: String): Unit
+