Add cl_ext_immutable_memory_objects tests writing to and from buffer (#2432)

This change extends the test coverage for
https://github.com/KhronosGroup/OpenCL-Docs/pull/1280

The change tests:
1. Writing to immutable buffers.
2. Writing to buffer/image from immutable buffers.
3. Reading from immutable buffers.

This change adds the following tests:
1. `test_negative_imagearraycopy`
2. `test_negative_imagearraycopy3d`
3. `test_immutable_bufferreadwriterect`
4. `test_immutable_arrayreadwrite`
5. `test_write_from_immutable_buffer_to_buffer`
6. `test_immutable_buffer_map_*`

and extends the following tests:
1. `test_arrayimagecopy3d`
2. `test_arrayimagecopy`
3. `test_imagearraycopy3d`
4. `test_imagearraycopy`
5. `test_buffer_copy`
6. `test_buffer_partial_copy`

Signed-off-by: Michael Rizkalla <michael.rizkalla@arm.com>

test_conformance/buffers/testBase.h

@@ -25,6 +25,6 @@
 extern const cl_mem_flags flag_set[];
 extern const char* flag_set_names[];
 
-#define NUM_FLAGS 5
+#define NUM_FLAGS 8
 
 #endif // _testBase_h