[llvm] [llvm-objdump] Add preliminary support for decoding binary files (PR #115667)

[Fangrui Song via llvm-commits]

MaskRay wrote:

```
binutils - objdump -D -bbinary -mi386:x86-64 -Mintel test.bin
this patch - llvm-objdump -d -b --triple x86_64 -Mintel test.bin
```

If we want to make the option similar, `-b` can be implemented as an option that only supports `binary` as the value (in GNU objdump, we can use `-bbinary` and `-bwasm` (supported only added around 2017?) and `-b elf64-x86-64`, but nobody seems to use `-belf64-x86-64`).

https://github.com/llvm/llvm-project/pull/115667