Add test for pointer to constant memory allocation

This isn't related to issue 3904. In codegen_alloc_pointer, the GlobalAlloc::from call returns GlobalAlloc::Memory, so we already codegened it as a constant allocation prior to this PR.
But I thought it would be good to have a test that exercises this case explicitly, and that demonstrates the difference between this case and the nested statics case, so I added it in this PR.

Author: Carolyn Zech

tests/kani/Static/pointer_to_const_alloc.rs

@@ -0,0 +1,24 @@
+// Copyright Kani Contributors
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// Test that Kani can codegen statics that contain pointers to constant allocations.
+// Test taken from https://github.com/rust-lang/rust/issues/79738#issuecomment-1946578159
+
+// alloc4 (static: BAR, size: 16, align: 8) {
+//     ╾─────alloc3<imm>─────╼ 01 00 00 00 00 00 00 00 │ ╾──────╼........
+// }
+
+// alloc3 (size: 4, align: 4) {
+//     2a 00 00 00                                     │ *...
+// }
+
+// alloc1 (static: FOO, size: 16, align: 8) {
+//     ╾─────alloc3<imm>─────╼ 01 00 00 00 00 00 00 00 │ ╾──────╼........
+// }
+pub static FOO: &[i32] = &[42];
+pub static BAR: &[i32] = &*FOO;
+
+#[kani::proof]
+fn main() {
+    assert_eq!(FOO.as_ptr(), BAR.as_ptr());
+}