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/FakeOverrideInAnonymousWithDelegation.sig.kt.txt

@@ -46,7 +46,6 @@ class Wrapper {
 //   Mangled name: Bar
 //   Public signature: /Bar|null[0]
 interface Bar {
-
   // CHECK:
   //   Mangled name: Bar{}foo
   //   Public signature: /Bar.foo|1688079488202778848[0]