Add test for size_of_val::<str>.
Add test for size_of_val::<str>.

GBGamer/rust,GBGamer/rust,tsion/miri,rust-lang/miri,rust-lang/miri,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,rust-lang/miri,rust-lang/miri