[neurun] Fix test directory structure (#2240)

Move graph test sources to `test/graph` so it will look identical to
`src` directory.

Signed-off-by: Hanjoung Lee <hanjoung.lee@samsung.com>

diff --git a/runtimes/neurun/test/Graph.cc b/runtimes/neurun/test/graph/Graph.cc
similarity index 100%
rename from runtimes/neurun/test/Graph.cc
rename to runtimes/neurun/test/graph/Graph.cc

diff --git a/runtimes/neurun/test/Index.cc b/runtimes/neurun/test/graph/Index.cc
similarity index 100%
rename from runtimes/neurun/test/Index.cc
rename to runtimes/neurun/test/graph/Index.cc

diff --git a/runtimes/neurun/test/operand/IndexSet.cc b/runtimes/neurun/test/graph/operand/IndexSet.cc
similarity index 100%
rename from runtimes/neurun/test/operand/IndexSet.cc
rename to runtimes/neurun/test/graph/operand/IndexSet.cc

diff --git a/runtimes/neurun/test/operand/Set.cc b/runtimes/neurun/test/graph/operand/Set.cc
similarity index 100%
rename from runtimes/neurun/test/operand/Set.cc
rename to runtimes/neurun/test/graph/operand/Set.cc

diff --git a/runtimes/neurun/test/operation/Set.cc b/runtimes/neurun/test/graph/operation/Set.cc
similarity index 100%
rename from runtimes/neurun/test/operation/Set.cc
rename to runtimes/neurun/test/graph/operation/Set.cc