Remastering of documentation provider

- Remove whole file resolve
- Take already resolved element
- Get kotlin element behind the wrapper directly
- Remove outdated isKotlinDeclaration method
- More tests

idea/testData/editor/quickDoc/AtVariableDeclaration.kt

@@ -0,0 +1,8 @@
+fun some() : String? = null
+
+fun test() {
+    val <caret>test = some()
+}
+
+
+//INFO: <b>val</b> test: jet.String? <i>defined in</i> test