OvmfPkg: pull in SMM-based variable driver stack

OvmfPkg: pull in SMM-based variable driver stack

When -D SMM_REQUIRE is given, replace both
- OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf and
- OvmfPkg/EmuVariableFvbRuntimeDxe/Fvb.inf
with
- OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesSmm.inf.

The outermost (= runtime DXE driver) VariableSmmRuntimeDxe enters SMM, and
the rest:
- the privileged half of the variable driver, VariableSmm,
- the fault tolerant write driver, FaultTolerantWriteSmm,
- and the FVB driver, FvbServicesSmm,
work in SMM purely.

We also resolve the BaseCryptLib class for DXE_SMM_DRIVER modules, for the
authenticated VariableSmm driver's sake.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19065 6f19259b-4bc3-4df7-8a09-765794883524