Prevent copy calls from repeat events of ctrl + c

now, even if user hold down ctrl + c on text controller,
copy will only be called once.

The patch below was added for this behavior.
https://review.tizen.org/gerrit/#/c/platform/core/uifw/dali-core/+/298930/
https://review.tizen.org/gerrit/#/c/platform/core/uifw/dali-adaptor/+/298931/

Change-Id: I521f4ad3baa5270f5fde0e484e27885b9a75e077
Signed-off-by: Bowon Ryu <bowon.ryu@samsung.com>