A new lint for shared code in if blocks

* Added expression check for shared_code_in_if_blocks
* Finishing touches for the shared_code_in_if_blocks lint
* Applying PR suggestions
* Update lints yay
* Moved test into subfolder

tests/ui/checked_unwrap/complex_conditionals.rs

@@ -1,5 +1,5 @@
 #![deny(clippy::panicking_unwrap, clippy::unnecessary_unwrap)]
-#![allow(clippy::if_same_then_else)]
+#![allow(clippy::if_same_then_else, clippy::shared_code_in_if_blocks)]
 
 fn test_complex_conditions() {
     let x: Result<(), ()> = Ok(());