Auto merge of #10949 - y21:issue8010, r=Alexendoo

[`manual_filter_map`]: lint on `matches` and pattern matching

Fixes #8010

Previously this lint only worked specifically for a very limited set of methods on the filter call (`.filter(|opt| opt.is_some())` and `.filter(|res| res.is_ok())`). This PR extends it to also recognize `matches!` in the `filter` and pattern matching with `if let` or `match` in the `map`.

Example:
```rs
enum Enum {
  A(i32),
  B,
}

let _ = [Enum::A(123), Enum::B].into_iter()
  .filter(|x| matches!(x, Enum::A(_)))
  .map(|x| if let Enum::A(s) = x { s } else { unreachable!() });
```
Now suggests:
```diff
-  .filter(|x| matches!(x, Enum::A(_))).map(if let Enum::A(s) = x { s } else { unreachable!() })
+  .filter_map(|x| match x { Enum::A(s) => Some(s), _ => None })
```

Adding this required a somewhat large change in code because it originally seemed to be specifically written with only method calls in the filter in mind, and `matches!` has different behavior in the map, so this new setup should make it possible to support more "generic" cases that need different handling for the filter and map calls.

changelog: [`manual_filter_map`]: lint on `matches` and pattern matching (and some internal refactoring)

clippy_utils/src/higher.rs

@@ -138,6 +138,7 @@ impl<'hir> IfLet<'hir> {
 }
 
 /// An `if let` or `match` expression. Useful for lints that trigger on one or the other.
+#[derive(Debug)]
 pub enum IfLetOrMatch<'hir> {
     /// Any `match` expression
     Match(&'hir Expr<'hir>, &'hir [Arm<'hir>], MatchSource),