Rollup merge of #100460 - cuviper:drop-llvm-12, r=nagisa

Update the minimum external LLVM to 13

With this change, we'll have stable support for LLVM 13 through 15 (pending release).
For reference, the previous increase to LLVM 12 was #90175.

r? `@nagisa`

Author: matthiaskrgr

core/src/cmp.rs

@@ -1139,11 +1139,7 @@ pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> {
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn le(&self, other: &Rhs) -> bool {
-        // Pattern `Some(Less | Eq)` optimizes worse than negating `None | Some(Greater)`.
-        // FIXME: The root cause was fixed upstream in LLVM with:
-        // https://github.com/llvm/llvm-project/commit/9bad7de9a3fb844f1ca2965f35d0c2a3d1e11775
-        // Revert this workaround once support for LLVM 12 gets dropped.
-        !matches!(self.partial_cmp(other), None | Some(Greater))
+        matches!(self.partial_cmp(other), Some(Less | Equal))
     }
 
     /// This method tests greater than (for `self` and `other`) and is used by the `>` operator.