Cache enhancements

This release adds new methods to the SortKeyCache interface:

1. prune - allows to remove old cache entries - https://github.com/warp-contracts/warp/blob/main/src/cache/SortKeyCache.ts#L65
2. delete - allows to remove all cached values for a given contract - https://github.com/warp-contracts/warp/blob/main/src/cache/SortKeyCache.ts#L35

What's Changed

• Implement prune method by @janekolszak in #268
• Delete method by @janekolszak in #281
• Lazy initialization of the LevelDB cache by @janekolszak in #282

New Contributors

• @janekolszak made their first contribution in #268

Full Changelog: v1.2.30...1.2.31