[llvm-readobj] Add --coff-tls-directory flag to print TLS Directory & test.

Akin to dumpbin's /TLS option, this will print out the TLS directory, if
present, in the image.

Example output:
```
> llvm-readobj --coff-tls-directory test.exe
File: test.exe
Format: COFF-x86-64
Arch: x86_64
AddressSize: 64bit
TLSDirectory {
  StartAddressOfRawData: 0x140004000
  EndAddressOfRawData: 0x140004040
  AddressOfIndex: 0x140002000
  AddressOfCallBacks: 0x0
  SizeOfZeroFill: 0x0
  Characteristics [ (0x0)
  ]
}
```

Reviewed By: jhenderson, grimar

Differential Revision: https://reviews.llvm.org/D88635