[test] Add some test assertions for `RandomBeaconHistory`'s usage

[m-Peter]

Closes https://github.com/onflow/cadence-tools/issues/261

Description

Add some assertions to verify the proper functionality of the RandomBeaconHistory built-in contract.

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• [x] Targeted PR against master branch
• [x] Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• [x] Code follows the standards mentioned here
• [x] Updated relevant documentation
• [x] Re-reviewed Files changed in the Github PR explorer
• [x] Added appropriate labels