Add missing assembly instruction to the x86 backend

[Arnau478]

The x86 backend was missing some important instructions. They're not generated by the compiler, but having them ensures they can be used in inline assembly. Added tests for all of them. Control registers where also added. A list of added instructions:

• rdmsr
• wrmsr
• sysret
• cmc
• clc
• stc
• cli
• sti
• cld
• std

Fixes #19773