[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/suspendConversionInVararg.sig.kt.txt

@@ -0,0 +1,15 @@
+// CHECK:
+//   Mangled name: #testSuspendConversionInVarargElementsAll(kotlin.Function0<kotlin.Unit>;kotlin.Function0<kotlin.Unit>;kotlin.Function0<kotlin.Unit>){}
+//   Public signature: /testSuspendConversionInVarargElementsAll|7160265821198055848[0]
+fun testSuspendConversionInVarargElementsAll(f1: Function0<Unit>, f2: Function0<Unit>, f3: Function0<Unit>): Unit
+
+// CHECK:
+//   Mangled name: #testSuspendConversionInVarargElementsSome(kotlin.Function0<kotlin.Unit>;kotlin.coroutines.SuspendFunction0<kotlin.Unit>;kotlin.Function0<kotlin.Unit>){}
+//   Public signature: /testSuspendConversionInVarargElementsSome|1432579013054877862[0]
+fun testSuspendConversionInVarargElementsSome(f1: Function0<Unit>, sf2: SuspendFunction0<Unit>, f3: Function0<Unit>): Unit
+
+// CHECK:
+//   Mangled name: #useSuspendVararg(kotlin.Array<out|kotlin.coroutines.SuspendFunction0<kotlin.Unit>>...){}
+//   Public signature: /useSuspendVararg|6945312118968967398[0]
+fun useSuspendVararg(vararg sfn: SuspendFunction0<Unit>): Unit
+