Rollup merge of #100820 - WaffleLapkin:use_ptr_is_aligned_methods, r=scottmcm

Use pointer `is_aligned*` methods

This PR replaces some manual alignment checks with calls to `pointer::{is_aligned, is_aligned_to}` and removes a useless pointer cast.

r? `@scottmcm`

_split off from #100746_

library/std/src/lib.rs

@@ -296,6 +296,7 @@
 #![feature(panic_can_unwind)]
 #![feature(panic_info_message)]
 #![feature(panic_internals)]
+#![feature(pointer_is_aligned)]
 #![feature(portable_simd)]
 #![feature(prelude_2024)]
 #![feature(provide_any)]