fix generic_address_space, command_buffer_event_sync, test_compiler and images/test_1D_buffer (#2062)

fixes several issues:

* `generic_address_space` test: add check for program scope variables.
The test uses both generic AS and program-scope variables, however it
only checked the generic-AS presence in `clGetDeviceInfo`.
* `compiler/test_compiler_defines_for_extensions.cpp`: add
`cl_khr_command_buffer_multi_device` to the list of recognized
extensions
* `command_buffer_event_sync.cpp`: add delays for testing
`clSetEventCallback` - according to specification, these can be executed
asynchronously (in a separate thread) by the OpenCL implementation,
hence the event callback is not quaranteed to be called before
`clFinish()` returns. Existing test `events/test_callbacks.cpp` also
waits for callback with loops of usleep.
* `images/kernel_image_methods/test_1D_buffer.cpp`: fix allocation size
being too small for the 1D buffer backing the image

---------

Co-authored-by: Ben Ashbaugh <ben.ashbaugh@intel.com>

test_conformance/compiler/test_compiler_defines_for_extensions.cpp

@@ -20,6 +20,7 @@
 #include <unistd.h>
 #endif
 
+// clang-format off
 // List should follow order in the extension spec
 const char *known_extensions[] = {
     "cl_khr_byte_addressable_store",
@@ -92,7 +93,9 @@ const char *known_extensions[] = {
     "cl_khr_external_memory_dma_buf",
     "cl_khr_command_buffer",
     "cl_khr_command_buffer_mutable_dispatch",
+    "cl_khr_command_buffer_multi_device"
 };
+// clang-format on
 
 size_t num_known_extensions = ARRAY_SIZE(known_extensions);
 size_t first_API_extension = 32;