[llvm] [MC, X86] emitInstruction: remove virtual function calls due to Intel JCC Erratum (PR #96835)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> ./llvm/test/MC/X86/align-branch-single.s

Thanks for the review! Added the test in a separate commit before this PR is merged.

https://github.com/llvm/llvm-project/pull/96835