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/candidateSymbol.kt.txt

@@ -25,7 +25,6 @@ abstract class AbstractFirBasedSymbol<E> where E : FirSymbolOwner<E>, E : FirDec
 }
 
 interface FirDeclaration {
-
 }
 
 interface FirSymbolOwner<E> where E : FirSymbolOwner<E>, E : FirDeclaration {