Interleave CC data for 23.976fps video to maintain 30/1.001 pairs per second

Changes how caption's timings are calculated for 23.976fps in accordance with the CEA-708-B standard.

When the option is turned on, 3 pairs of CC data will be encoded for every other frame. And when it's turned off - 2 pairs of CC data will be encoded for every video frame. Or in other words, turning the option on allows 25% more text to be decoded over the same period of time which also accounts for decreasing the "time to process" required for each caption.

Note: This option is available only when the project is configured for 23.976fps. Whether it's clicked on or off by default depends on how the same option is configured at the Project Settings/Safe Area menu. We don't recommend turning the option on when it isn't turned on in the Project Settings. And vise-versa.