[obj2yaml] - Teach tool to emit the "SectionHeaderTable" key and sort sections by...

[obj2yaml] - Teach tool to emit the "SectionHeaderTable" key and sort sections by file offset.

Currently when we dump sections, we dump them in the order,
which is specified in the sections header table.

With that the order in the output might not match the order in the file.
This patch starts sorting them by by file offsets when dumping.

When the order in the section header table doesn't match the order
in the file, we should emit the "SectionHeaderTable" key. This patch does it.

Differential revision: https://reviews.llvm.org/D91249