Add plandomized_locations as a presets option

[Elagatua]

Adds support for a plandomized_locations dictionary in a settings preset. This dictionary takes a map of locations and items and adds it to the distribution before the seed is rolled.

Example that forces Link to start with the Light Medallion:

"plandomized_locations": {
    "Links Pocket": "Light Medallion"
},

[fenhl]

This is well-tested as part of Triforce Blitz season 3.