[video_player] Remove Ecore API

[gin7773]

Main changes:

• Replace Ecore API with glib API.

#1032

[gemini-code-assist]

Code Review

This pull request replaces the Ecore API with GLib APIs for event dispatching and screensaver timeout management in the Tizen video player implementation. Feedback on these changes identifies potential deadlocks from lock order inversion in PushEvent and SendError, a potential resource leak of main_context_ if construction fails, and a potential GLib warning if timer_id_ is not properly reset upon source destruction.

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