Deserialization of inline (value) classes should be properly handled

[orchestr7]

Right now the following deserialisation is not supported:

class InlineDecoderTest {
    @JvmInline
    @Serializable
    value class Color(val rgb: Long)

    @Test
    fun testDecodingWithCustomSerializer() {
            Toml.decodeFromString<Color>(
            """
                rgb = 0
            """.trimIndent()
            )
    }
}

This happens, because of a missing implementation for public fun decodeInline(inlineDescriptor: SerialDescriptor): Decoder
method and invalid traversing of AST:

Invalid call to getNeighbourNodes() for TomlFile node
com.akuleshov7.ktoml.exceptions.InternalAstException: Invalid call to getNeighbourNodes() for TomlFile node
	at app//com.akuleshov7.ktoml.tree.TomlFile.getNeighbourNodes(TomlFile.kt:17)
	at app//com.akuleshov7.ktoml.decoders.TomlMainDecoder.getCurrentNode(TomlMainDecoder.kt:65)
	at app//com.akuleshov7.ktoml.decoders.TomlMainDecoder.decodeKeyValue$ktoml_core(TomlMainDecoder.kt:76)
	at app//com.akuleshov7.ktoml.decoders.TomlAbstractDecoder.decodeLong(TomlAbstractDecoder.kt:83)