[llvm-readobj][llvm-readelf][test] - Add a few more dynamic section tests.

This adds a few more tests for dynamic section.

We only had tests for simple unknown values for 64-bits target,
in this patch I've added OS specific and processor specific tags.
Also it tests both 32 and 64-bits targets now.

It will help to fix the formatting issues we have and diagnose a possible new ones.

Differential revision: https://reviews.llvm.org/D71896