[AMDGPU][True16][test] update VOPC/VOPCX test for true16/fake16

[broxigarchen]

This is a non-functional change

update GFX11/GFX12 VOPC/VOPCX asm/dasm test for true16/fake16:

1. duplicate files to be true16/fake16 by adding "-mattr=+real-true16/-mattr=-real-true16" while true16 test file will be updated to true16 format when the true16 instructions are supported
2. sort "*t16_err.s" and "*t16_promote.s" tests to alphabetic order. tests to alphabetic order. This is for the upcoming true16 mc changes, and mainly trying to help repo maintainer to resolve conflicts in the tests quickly. A script is proposed to help for the sorting https://github.com/llvm/llvm-project/pull/111769. Since these two files are t16 only, it should not create conflicts in downstream branches
3. add -filetype=null to seperate stdout and stderr to avoid disordered output from llvm-mc