[BUGFIX] Improvements to the save data system to prevent overwriting when resolution fails.

[EliteMasterEric]

Does this PR close any issues? If so, link them below.

#3679

Briefly describe the issue(s) fixed.

• Replaced all Enum fields with Enum Abstract fields.
• Incremented the Save data version to 2.1.0 (since this is a breaking change) and implemented migration.
  • Older versions of the game will now complain that the save data is too new when trying to load.
  • Had to create some dummy enums in the save data migrator to prevent errors from loading older saves.
• In the event that the save data fails to parse, the game will now display a big warning popup telling the user to report the issue. It will then create a new save, leaving the broken save in place.

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