Get Blizzard implement API for querying content phase.

This would help Questie determine what quests to show without hardcoding phases or trying to find out phase by other means. It would allow much better UX as data would assumable be already available at addon load process. And it would avoid many bug reports for Questie I can see coming.

Link to already closed issue, which seemt to add only querying current season: Stanzilla/WoWUIBugs#189

This is definitely stale, but as we gain more of a grasp for how seasons will happen in the future, I'll reach out to contacts to see if we could get this added. One initial issue that we saw from Season of Mastery's launch is that some content followed a phased release cycle, but not all of it did; content was actually released out of order. For instance, Dire Maul was available in SoM at launch, but world bosses came in a later phase, and (more importantly as it relates to Questie), the entire tier 0.5 questline was available at launch, not released alongside the AQ phase. In essence, this meant that the only quests locked behind phases were ones directly related to their corresponding raid. We would need to know three variables:

1. is this a seasonal server, already implemented with C_Seasons.HasActiveSeason()
2. which season is this, already implemented with C_Seasons.GetActiveSeason()
3. which content phase of the corresponding season from C_Seasons.GetActiveSeason() are we currently in - this one is not implemented, and would need to be established ahead of time with Blizzard to know what variables correspond to what content, since (like with SoM) it may change from season to season.

I expect we'll hear more about a future season at Blizzcon 2023, and if we do, I'll press for this.