[BOLT] Mark fragments related to split jump table as non-simple

[BOLT] Mark fragments related to split jump table as non-simple

Mark fragments related to split jump table as non-simple.

A function could be splitted into hot and cold fragments. A split jump table is
challenging for correctly reconstructing control flow graphs, so it was marked
as ignored. This update marks those fragments as non-simple, allowing them
to be printed and partial control flow graph construction.

Test Plan:
```
llvm-lit -a tools/bolt/test/X86/split-func-icf.s
```
This test has two functions (main, main2), each has a jump table target to the
same cold portion main2.cold.1(*2). We try to print out only this cold portion.
If it is ignored, it cannot be printed. If it is non-simple, it can be printed. We
verify that it can be printed.

Reviewed By: Amir

Differential Revision: https://reviews.llvm.org/D127464