Fix Decoder not representing the current node correctly

[Jojo4GH]

First bug from https://github.com/charleskorn/kaml/pull/607

Previously the node property on the decoders was not traversed in deep YAML trees (e.g. with YamlMapLikeInputBase and YamlListInput). This behaviour is different from the JSON serialization library and makes it impossible to implement a content based polymorphic KSerializer in a meaningful way without knowing of the whole YAML tree. See also the DecodingFromYamlNodeSerializer in YamlReadingTest.kt for an affected case