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/firProblems/SignatureClash.kt.txt

@@ -17,7 +17,6 @@ object Factory {
 }
 
 interface Base {
-
 }
 
 interface Delegate : Base {
@@ -26,7 +25,6 @@ interface Delegate : Base {
 }
 
 interface Derived : Delegate {
-
 }
 
 data class DataClass : Derived, Delegate {