Add regression test

Author: LeSeulArtichaut

src/test/ui/lint/issue-69173-unsafe-block-in-unsafe-fn.rs

@@ -0,0 +1,11 @@
+// Regression test for #69173: do not warn for `unsafe` blocks in `unsafe` functions
+
+// check-pass
+
+#![allow(dead_code)]
+#![deny(unused_unsafe)]
+
+unsafe fn foo() {}
+unsafe fn bar() { unsafe { foo(); } }
+
+fn main() {}