feat(api): add API_GetUserAwards endpoint

[wescopeland]

This PR adds a new endpoint, API_GetUserAwards.php.

Why?

While it is currently possible to fetch a user's game completion stats with API_GetUserCompletedGames, this does not actually neatly map to what game awards a user has. For example, if a game has added new achievements in the months/years since the game was mastered by the user, it is not possible using the existing endpoint to know if a given user actually earned a mastery from the game.

This leads to awkward situations where a Discord bot might announce "User X just unlocked their 25th mastery!", when actually they got their 25th mastery years ago.

How?

GET https://retroachievements.org/API/API_GetUserAwards.php?z=...&y=...&u=SomeUser

{
  TotalAwardsCount: 14,
  HiddenAwardsCount: 9,
  MasteryAwardsCount: 9,
  CompletionAwardsCount: 1,
  EventAwardsCount: 0,
  SiteAwardsCount: 3,
  VisibleUserAwards: [
    {
      AwardedAt: '2014-09-29T12:41:48+00:00',
      AwardType: 'Mastery/Completion',
      AwardData: 504,
      AwardDataExtra: 0,
      DisplayOrder: 0,
      Title: 'Super Mario Land',
      ConsoleName: 'Game Boy',
      Flags: null,
      ImageIcon: '/Images/060955.png',
    },
    ...
  ],
};

Implementation Details

• I have converted the existing mysqli stuff for fetching user site awards to use the new legacyDbFetch* functions.
• I have written tests for the new endpoint.
• Metadata for hidden awards is not exposed via this endpoint.