perf: Make kura drop old blocks from memory

[dima74]

Context

Meta: #5083 Fixes #4954

Solution

Currently kura stores all blocks in memory, which results in memory usage approximately 1.6KB per transaction, or 1.6GB per 1 million transactions. This PR changes to store only N last blocks in memory (128 by default). Other blocks will be loaded from the disk if needed. This improves memory usage to approximately 280 bytes per transaction or 0.26GB per 1 million transactions. Note that memory usage is still unbounded because of State::transactions map.

Checklist

• [ ] I've read CONTRIBUTING.md.
• [ ] (optional) I've written unit tests for the code changes.
• [ ] All review comments have been resolved.
• [ ] All CI checks pass.

[SamHSmith]

I broke DCO by pushing the rebase button. Please rebase locally and then force push so that we can merge.