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/contextReceivers/fromKEEP/canvas.sig.kt.txt

@@ -24,7 +24,6 @@ class Circle : Shape {
 //   Mangled name: Canvas
 //   Public signature: /Canvas|null[0]
 interface Canvas {
-
   // CHECK:
   //   Mangled name: Canvas{}suffix
   //   Public signature: /Canvas.suffix|-3301965527200666288[0]
@@ -46,7 +45,6 @@ interface Canvas {
 //   Mangled name: Shape
 //   Public signature: /Shape|null[0]
 interface Shape {
-
   // CHECK JVM_IR:
   //   Mangled name: Shape#draw!Canvas(){}kotlin.String
   //   Public signature: /Shape.draw|-6733499063990640842[0]

compiler/testData/ir/irText/declarations/contextReceivers/fromKEEP/compareTo.sig.kt.txt

@@ -37,6 +37,7 @@ data class Pair<A : Any?, B : Any?> {
   //   Public signature: /Pair.<init>|3086114026882374588[0]
   //   Public signature debug description: <init>(1:0;1:1){}
   constructor(first: A, second: B) /* primary */
+
   // CHECK JVM_IR:
   //   Mangled name: Pair#component1(){}1:0
   //   Public signature: /Pair.component1|2393470133763651536[0]

compiler/testData/ir/irText/declarations/contextReceivers/fromKEEP/monoidSum.sig.kt.txt

@@ -33,7 +33,6 @@ interface Monoid<T : Any?> : Semigroup<T> {
 //   Mangled name: Semigroup
 //   Public signature: /Semigroup|null[0]
 interface Semigroup<T : Any?> {
-
   // CHECK JVM_IR:
   //   Mangled name: Semigroup#combine@1:0(1:0){}1:0
   //   Public signature: /Semigroup.combine|-3517256775590682507[0]