Fix include-what-you-use issues

[derobins]

IWYU is generally quiet after this patch, aside from:

• Google Test headers being declared local
• One instance of mountinfo.h being declared a system header
• IWYU wants to strip stdbool.h from hipfile.h and rocfile.h since it's running a C++ compiler

We can try to handle this later in a mapping file.

[derobins]

Fun fact: hip/hip_runtime_api.h MUST come before hip/driver_types.h because the latter is not self-contained.

[derobins]

FWIW, IWYU has a lot of bad ideas about C vs C++ and system vs local headers. It's not ready for being a GitHub CI action and we should definitely not use the auto-fix tool.

[kurtmcmillan]

If IWYU is not part of CI should we add a contributions guide stating that contributors should run IWYU for each commit?