Adding MC regressions tests to cover the CET instructions.
This patch is part of a larger task to cover MC encoding of all X86 isa sets started in revision: https://reviews.llvm.org/D39952
I added encoding test in the following review:
cet-encoding.s checks only 64 bit encoding of all CET instructions (IBT and SHSTK).
Since all instructions that are supported in 32 bit, are also supported in 64 bit, I am not sure 32 bit encoding test is required.
If you do think it is needed, there are some instructions that are missing in your test: incspp, endbr64, endbr32 and setssbsy.
For more information on CET, please read section 6 in the following document: