client/container: root: refactor common namespace

- Factor out respective common from macro and apply to all scopes
  * `dfi::common`
  * `dfi::macro::common`
  * `dfi::plugin::common`

- Add deprecation warnings in `dfi::macro::common`
  * Common functionality (not macro specific) is now in `dfi::common`

- Add convenience wrappers to inner common impl, where appropriate
  * Allows for backwards compatibility

- Add/update/clarify code docs and Doxygen definitions

- Related refactoring

NOTE: all changes are backward compatible (no need to bump major).

container/src/root/macro/test/benchmark.C

@@ -28,7 +28,7 @@
 #include <initializer_list>
 #include <string>
 
-#include "../common/utility.hh"
+#include "../../common/utility.hh"
 
 //! \namespace dfi
 //! \since docker-finance 1.0.0
@@ -70,10 +70,9 @@ class Benchmark
         {"../test/benchmark/random.hh"},
         {"../test/benchmark/utility.hh"}};
 
-    namespace common = ::dfi::macro::common;
     if (!loaded)
       {
-        common::Command::load(paths);
+        ::dfi::common::Command::load(paths);
         loaded = true;
       }
 

container/src/root/macro/test/unit.C

@@ -28,7 +28,7 @@
 #include <initializer_list>
 #include <string>
 
-#include "../common/utility.hh"
+#include "../../common/utility.hh"
 
 //! \namespace dfi
 //! \since docker-finance 1.0.0
@@ -71,10 +71,9 @@ class Unit
         {"../test/unit/type.hh"},
         {"../test/unit/utility.hh"}};
 
-    namespace common = ::dfi::macro::common;
     if (!loaded)
       {
-        common::Command::load(paths);
+        ::dfi::common::Command::load(paths);
         loaded = true;
       }