Add reduced crasher for SR-7958

Trying to use an argument label in an interpolation can cause various crashes. In swiftlang-1000.0.16.7, these are usually in SILGen; in master at 8f6028d, they’re in CSApply.

Author: beccadax

validation-test/compiler_crashers_2/0160-sr7958.swift

@@ -0,0 +1,10 @@
+// RUN: %target-swift-frontend -emit-silgen %s
+
+func foo<U>(_ x: U?) {
+  _ = "\(anyLabelHere: x)"
+}
+
+// This one also crashes in a slightly different place
+func bar(_ x: Int?) {
+  _ = "\(anyLabelHere: x)"
+}