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/classes/dataClasses/dataClasses.sig.kt.txt

@@ -52,6 +52,7 @@ data class Test1 {
   //   Public signature: /Test1.<init>|3237794121889594884[0]
   //   Public signature debug description: <init>(kotlin.Int;kotlin.String;kotlin.Any){}
   constructor(x: Int, y: String, z: Any) /* primary */
+
   // CHECK JVM_IR:
   //   Mangled name: Test1#component1(){}kotlin.Int
   //   Public signature: /Test1.component1|-8217597213800111288[0]
@@ -148,6 +149,7 @@ data class Test2 {
   //   Public signature: /Test2.<init>|-8205545948568413246[0]
   //   Public signature debug description: <init>(kotlin.Any?){}
   constructor(x: Any?) /* primary */
+
   // CHECK JVM_IR:
   //   Mangled name: Test2#component1(){}kotlin.Any?
   //   Public signature: /Test2.component1|-9062417290864755441[0]
@@ -269,6 +271,7 @@ data class Test3 {
   //   Public signature: /Test3.<init>|8878758829470622568[0]
   //   Public signature debug description: <init>(kotlin.Double;kotlin.Double?;kotlin.Float;kotlin.Float?){}
   constructor(d: Double, dn: Double?, f: Float, df: Float?) /* primary */
+
   // CHECK JVM_IR:
   //   Mangled name: Test3#component1(){}kotlin.Double
   //   Public signature: /Test3.component1|2948120330742694173[0]