refactor(map)!: migrate BaseMap to record and improve map loading

[theEvilReaper]

Proposed changes

The map-related code has been modernized in some areas to improve game setup implementations. However, the core logic remains unchanged and currently relies on duplicate method definitions. This pull request migrates the BaseMap class into a record, removing its mutable nature. Creating a new map must now be done via the BaseMapBuilder.

In addition, the AbstractMapProvider has been updated to improve null checks and related behavior. The internal list storing MapEntry instances is now instantiated by default as an empty list. During loading, each entry is added to this list. Note that if loading is triggered multiple times, all existing entries will be cleared before being added again.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

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• I have read the CONTRIBUTING.md
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)