display: display-state-transition: Relocate fuctions related to transition timer...

display: display-state-transition: Relocate fuctions related to transition timer to reduce plugin duplication

Remove and redefine get_transition_timer()/timeout_handler()/reset_timeout() in plugins/display/core.c

These function are added to below display-state-transition.c
bool display_state_transition_is_there_state_transition_timer(void);
int display_state_transition_reset_state_transition_timeout(int timeout);
-> These are used to add and manage timeout callback for a specific state transition.

In fact, these functions do not actually change the time of the state transition.
They only generate state transitions by adding timeout callbacks.(with timeout parameter)
Thus, "reset" word or function name should be changed during refactoring process.

Change-Id: Icc4b70b7dd6bb30bd5bc5aa56d331cfe9fc726c6
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>