KotlinLineMarkerProvider: ignore non-leaf elements when putting gutters (KT-28075, KT-30052, KT-33182)

previously for instance `KtClassBody` could get here as `leaf` and `leaf.parent` will return `KtClass` for it, making gutter for `KtClass` appear twice if origingal identifier and `KtClassBody` got here in different passes (one in "inner" other in "outer")

idea/testData/multiModuleLineMarker/fromActualAnnotationWithParametersInOneLine/jvm/jvm.kt

@@ -3,10 +3,6 @@ actual annotation class <lineMarker descr="Has declaration in common module">Ann
         actual val <lineMarker descr="Has declaration in common module">z</lineMarker>: Double, actual val b: Boolean
 )
 
-// TODO: first marker on 'Ann' is generated twice here, see collectSlowLineMarkers main loop.
-// Since it's fragile place, I don't want to fix it right now
-
-
 /*
 LINEMARKER: Has declaration in common module
 TARGETS:
@@ -15,11 +11,6 @@ expect annotation class <1>Ann(
 *//*
 LINEMARKER: Has declaration in common module
 TARGETS:
-common.kt
-expect annotation class <1>Ann(
-*//*
-LINEMARKER: Has declaration in common module
-TARGETS:
 common.kt
         val <1>x: Int, val <2>y: String,
 *//*