Adding XP Gains to Battlegrounds (Warsong Gulch)

[i-am-fyre]

This PR provides the server with the functionality to offer XP as a reward in battlegrounds and provides the framework for other battlegrounds to be included.
This PR focuses on Warsong Gulch only. Three ways to earn XP:

1. Flag Capture (Pictured below as 1, 2, 3)
2. Remaining Flags at the end of the match. (Pictured below as 4, 5, 6 -- in this example, it was a 3-0 win for Horde, so 3 remaining flags.)
3. Win (Pictured below as 7)
   

Values for XP are an approximation and NOT Blizzlike. Using era appropriate videos, we extracted XP gains at different levels. The formula utilized in this PR does not match the values exactly, but does scale very closely.

Thank you to REGNURZA on Discord for identifying the lack of XP provided during battlegrounds and researching videos for XP gains!
Thank you to Neddings on Discord for also researching videos!
Thank you to Xenocide21 on Discord for help with upscaling videos/images!

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This change is 

[AppVeyorBot]

✅ Build Mangos TWO Server 22.02.89 completed (commit e335a0b4dc by @i-am-fyre)

[AppVeyorBot]

✅ Build Mangos TWO Server 22.02.90 completed (commit f4f00bd258 by @i-am-fyre)

[billy1arm]

@i-am-fyre would this be valid for any other cores?

[i-am-fyre]

@billy1arm XP gains from battlegrounds was implemented in 3.2.0 (https://wowpedia.fandom.com/wiki/Patch_3.2.0).

So it should be okay to port to M3+.
If we wanted to port the functionality to M0/M1 it should go behind a config.