[llvm] [X86][GlobalISel] Enable G_BRJT (PR #81811)

[Evgenii Kudriashov via llvm-commits]

https://github.com/e-kud commented:

@RemiSEGARD could you please add an end-to-end test e.g. `test/Target/X86/isel-brjt.ll` for all selectors similarly to other `isel-*.ll` tests.

https://github.com/llvm/llvm-project/pull/81811