[ADT] Add <cstdint> to SmallVector (llvm#101761)

SmallVector uses `uint32_t`, `uint64_t` without including `<cstdint>`
which fails to build w/ GCC 15 after a change in libstdc++ [0]

[0] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=3a817a4a5a6d94da9127af3be9f84a74e3076ee2

(cherry picked from commit 7e44305)

Author: thesamesam

llvm/include/llvm/ADT/SmallVector.h

@@ -19,6 +19,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
+#include <cstdint>
 #include <cstdlib>
 #include <cstring>
 #include <functional>