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/expressions/funInterface/samConversionsWithSmartCasts.fir.kt.txt

@@ -83,7 +83,6 @@ fun <T> test7b(a: T) where T : Function1<Int, Unit>, T : Function0<Unit> {
 }
 
 interface Unrelated {
-
 }
 
 fun <T> test7c(a: T) where T : Unrelated, T : Function0<Unit> {