The section headers for XCOFF files have a subtype flag for Dwarf
sections. This PR updates obj2yaml, yaml2obj, and llvm-readobj so that
they recognize the subtype.

XCOFF encodes a symbol type and alignment in a single 8-bit field. It is
easier to read and write YAML files if the fields can be specified
separately. This PR causes obj2yaml to write the fields separately and
allows yaml2obj to read either the single combined field or the separate
fields.

This PR adds the support for parsing auxiliary symbols of XCOFF object file for obj2yaml.

The sanitizer error is clean now.

This reverts commit 0e3faa20c467e6cd62423b22cf8650c6aa2628ba.

Due to a sanitizer error in https://lab.llvm.org/buildbot/#/builders/5/builds/39023.
Will be re-landed after repairs and thorough testing.

This PR adds the support for parsing auxiliary symbols of XCOFF object
file for obj2yaml.

Summary: The patch adds support for yaml2obj parsing auxiliary
symbols for XCOFF. Since the test cases of this patch are
interdependent with D113825 ([llvm-readobj][XCOFF] dump
auxiliary symbols), test cases of this patch will be committed
after D113825 is committed.

Reviewed By: jhenderson, DiggerLin

Differential Revision: https://reviews.llvm.org/D113552

Summary: Fix the build failure on MSVC by making the `T` and `U` of the function
'T llvm::Optional<T>::getValueOr<llvm::yaml::Hex32>(U &&) const &' the same.

Differential Revision: https://reviews.llvm.org/D111487

This is failing on MSVC builds: https://lab.llvm.org/buildbot/#/builders/86/builds/23436

Summary:
  This patch adds yaml2obj supporting for the auxiliary
  file header of XCOFF.

Reviewed By: DiggerLin, jhenderson

Differential Revision: https://reviews.llvm.org/D111487