Add regression test for stack overflow in redundant_pattern_matching

Author: flip1995

tests/ui/crashes/ice-7169.rs

@@ -0,0 +1,9 @@
+#[derive(Default)]
+struct A<T> {
+    a: Vec<A<T>>,
+    b: T,
+}
+
+fn main() {
+    if let Ok(_) = Ok::<_, ()>(A::<String>::default()) {}
+}

tests/ui/crashes/ice-7169.stderr

@@ -0,0 +1,10 @@
+error: redundant pattern matching, consider using `is_ok()`
+  --> $DIR/ice-7169.rs:8:12
+   |
+LL |     if let Ok(_) = Ok::<_, ()>(A::<String>::default()) {}
+   |     -------^^^^^-------------------------------------- help: try this: `if Ok::<_, ()>(A::<String>::default()).is_ok()`
+   |
+   = note: `-D clippy::redundant-pattern-matching` implied by `-D warnings`
+
+error: aborting due to previous error
+