Implement level.dat reading and load the seed for use in world generation #1464

Job	Run time
Run lints in release mode (stable)	49s
Run lints (stable)	1m 11s
Build project in release (ubuntu-latest, stable)	2m 5s
Build project and test (ubuntu-latest, stable)	6m 12s
Build project in release (windows-latest, stable)	4m 0s
Build project and test (windows-latest, stable)	12m 53s
Check formatting (stable)	5s
Build project in release (macos-latest, stable)	1m 43s
Build project and test (macos-latest, stable)	4m 41s
	33m 39s

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