OvmfPkg/AcpiPlatformDxe: consolidate #includes and [LibraryClasses]
    
    - #include only such public headers in "AcpiPlatform.h" that are required
      by the function declarations and type definitions introduced in
      "AcpiPlatform.h". Don't use "AcpiPlatform.h" as a convenience #include
      file.
    
    - In every file, list every necessary public #include individually, with
      an example identifier that's actually consumed.
    
    - Remove unnecessary lib classes, add unlisted lib classes.
    
    - Remove unnecessary #include directives, add unlisted #include
      directives.
    
    Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
    Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2122
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>