Rollup merge of #138041 - thaliaarchi:use-prelude-size-of.boostrap-compiletest, r=jieyouxu

bootstrap and compiletest: Use `size_of_val` from the prelude instead of imported

Use `std::mem::size_of_val` from the prelude instead of importing or qualifying it.

This function was added to all preludes in Rust 1.80.

r? ``@jieyouxu``

Author: compiler-errors