[DX] Create globals for DXContainer parts

DXContainer files have a handful of sections that need to be written.
This adds a pass to write the section data into IR globals, and writes
the shader flag data into a global.

The test cases here verify that the shader flags are correctly written
from the IR into the global and emitted to the DXContainer.

This change also fixes a bug in the MCDXContainerWriter, where the size
of the dxbc::ProgramHeader was not being included in the part offset
calcuations. This is verified to be working by the new testcases where
obj2yaml can properly dump part data for parts after the DXIL part.

Resolves issue #57742 (https://github.com/llvm/llvm-project/issues/57742)

Reviewed By: python3kgae

Differential Revision: https://reviews.llvm.org/D135793