Rollup merge of #140804 - bend-n:signed, r=lcnr

add signed ints to unn- transmutes to ensure feature parity

i forgot a few cases rust-lang/rust-clippy#14703

adds

- char -> i32
-  i32 -> char
- float -> size ()
-  size -> float
-   i32 -> float
``@rustbot`` label L-unnecessary_transmutes

Author: Zalathar

tests/pass/shims/x86/intrinsics-x86-sse2.rs

@@ -1,5 +1,6 @@
 // We're testing x86 target specific features
 //@only-target: x86_64 i686
+#![allow(unnecessary_transmutes)]
 
 #[cfg(target_arch = "x86")]
 use std::arch::x86::*;