IR text tests: Stable blank lines between declarations in class

Rework rendering of kt-like dump and signatures dump in order to avoid
unstable blank line between declarations of the same level:
1. No blank line for the first declaration inside the member scope of
the class.
2. Always a single blank line between each two subsequent declarations
inside the member scope of the class.

compiler/testData/ir/irText/declarations/annotations/genericAnnotationClasses.kt.txt

@@ -27,7 +27,6 @@ open annotation class Test2<T1 : Any, T2 : Any?> : Annotation {
 }
 
 interface I<T : Any?> {
-
 }
 
 open annotation class Test3<T1 : Any?, T2 : I<T1>> : Annotation {