Heimdall prepares the next span a number of sprints before the current
span ends. Currently we always fetch the next span regardless of which
sprint we are in during the current span. This causes a liveness issue
due to how the Heimdall client works (it infinitely retries until it
fetches a span - this issue will be fixed in a separate PR). This PR
fixes this by matching what bor does - it fetches the next span only in
the last sprint of the current span.
Changes:
- Adds a unit test for the above
- Adds a new function BlockInLastSprintOfSpan
- Some code reorg and cleanup - moves the span num related functions
from the bor package to the span sub package for better logical grouping
This PR adds support to store the transaction dependency (generated by
the block producer) in the block header for bor. This transaction
dependency will then be used by the parallel processor
([Block-STM](https://github.com/ledgerwatch/erigon/pull/7812/)).
I have created another
[PR](https://github.com/ledgerwatch/erigon-lib/pull/1064) in the
erigon-lib repo which adds the `IsParallelUniverse()` function.
System contract upgrades for Polygon are already handled by the
`BlockAlloc` logic and there's no need to duplicate it with the
`CalcuttaBlock` logic (there's no Calcutta in
https://github.com/maticnetwork/bor).
