- handle IMAGE_FILE_MACHINE_R4000 machine type
- handle MIPS COFF relocations

llvm-objdump can now parse MIPS COFF files.

This fixes:
```
[1304/6998] Building CXX object lib\ObjectYAML\CMakeFiles\LLVMObjectYAML.dir\COFFYAML.cpp.obj
C:\git\llvm-project\llvm\lib\ObjectYAML\COFFYAML.cpp(561): warning C4018: '<': signed/unsigned mismatch
```

There can be zero padding bytes at a section end for file alignment in
PECOFF. Exclude those padding bytes when reading the section data.

Differential Revision: https://reviews.llvm.org/D157059

Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D149440

Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D149439

Similar to D125411, but for ARM64X.

ARM64X PE binaries are hybrids containing both ARM64EC and pure ARM64
variants in one file. They are usually linked by passing separate
ARM64EC and ARM64 object files to linker. Linked binaries use ARM64
machine and contain additional CHPE metadata in their load config.
CHPE metadata support is not part of this patch, I plan to send that later.

Using ARM64X as a machine type of object files themselves is somewhat
ambiguous, but such files are allowed by MSVC. It treats them as ARM64
or ARM64EC object, depending on the context. Such objects can be
produced with cvtres.exe -machine:arm64x.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D148517

This is the first patch of a patchset to add initial support for
ARM64EC. Basic documentation is available at
https://docs.microsoft.com/en-us/windows/uwp/porting/arm64ec-abi .
(Discourse post:
https://discourse.llvm.org/t/initial-patches-for-arm64ec-windows-11-now-posted/62449
.)

The file format for ARM64EC is basically identical to normal ARM64.
There are a few extra sections, but the existing code for reading ARM64
object files just works.

Differential Revision: https://reviews.llvm.org/D125411

This makes it easy to write tests where the irrelevant fields are not needed.

Allow variable number of directories, as allowed by the
specification. NumberOfRvaAndSize will default to 16 if not specified,
as in the past.

Reviewed by: jhenderson

Differential Revision: https://reviews.llvm.org/D108825