Optimized 5 different buffers.

[shahzadlone]

Many vectors weren't being reserved where we already know the size.

This makes the vector re-allocate(expensive) more times than necessary.

I reserved the 5 vectors where we already knew how many elements will get pushed in.

I also reduced the scope of audio_samples,video_samples,edit_boxes because they were declared way earlier than they are actually used. (prefer to delay declaration, as much as possible.)

Also made edit_box a constant and a reference to save a copy cost and const because it isn't changed.

[CLAassistant]

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