vulkan: don't leak debug utils label name
What does this MR do and why?
vulkan: don't leak debug utils label name
Label names are duplicated, so free them before resetting or deleting
the cmdbuffer/queue.
Fixes leaks when testing dEQP-VK.api.debug_utils.long_labels.
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>