Rollup merge of #93751 - eholk:issue-93648-drop-tracking-projection, r=tmiasko

Drop tracking: track borrows of projections

Previous efforts to ignore partially consumed values meant we were also not considering borrows of a projection. This led to cases where we'd miss borrowed types which MIR expected to be there, leading to ICEs.

This PR also includes the `-Zdrop-tracking` flag from #93313. If that PR lands first, I'll rebase to drop the commit from this one.

Fixes #93648

src/test/ui/async-await/issue-93648.rs

@@ -0,0 +1,12 @@
+// edition:2021
+// build-pass
+// compile-flags: -Zdrop-tracking
+
+fn main() {
+    let _ = async {
+        let mut s = (String::new(),);
+        s.0.push_str("abc");
+        std::mem::drop(s);
+        async {}.await;
+    };
+}