cactus: adding memory sharing tests

Added tests to FF-A memory sharing interface. To enable them:
- The message loop was refactored to support multiple requests/commands
 coming through direct messaging, leveraging command wrappers
 from the previous commit.
 - Enabled adding dynamic memory regions to translation table, according
 to xlat_tables_v2 library documentation [1];
 - Mapped translation tables into cactus memory mapping so that they can
 be updated after a memory retrieve.

[1] https://trustedfirmware-a.readthedocs.io/en/latest/components/xlat-tables-lib-v2-design.html?highlight=xlat

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I73c9ba66dd89c53c50eca6ba6aca2e0ad115cb35
diff --git a/spm/cactus/cactus_tests.h b/spm/cactus/cactus_tests.h
index 2e13a6f..fd229bf 100644
--- a/spm/cactus/cactus_tests.h
+++ b/spm/cactus/cactus_tests.h
@@ -16,6 +16,10 @@
 /*
  * Test to FFA interfaces.
  */
+void ffa_memory_management_test(struct mailbox_buffers *mb, ffa_vm_id_t vm_id,
+				ffa_vm_id_t sender, uint32_t mem_func,
+				uint64_t handle);
+
 void ffa_tests(struct mailbox_buffers *mb);
 
 /*