Description of change

Move commitment checks to block's syntactical check.
Cleanup of block's and transaction's syntactical checks for APIv3.
Implement test to make sure that the validation works correctly.
Definition of minCommitableAge and maxCommitableAge is updated to take into account the current, unfinished slot. So for example, with minCommittableAge=10 and maxCommittableAge=20, a block issued in the middle of slot 100 can commit at most to 90 (100-10) and at least to slot 80 (100-20). Previously it was 89 and 79 respectively, because it meant 10 full slots, so we had to artificially add 1 to min/maxCommittableAge to get the correct value in most checks.

Type of change

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• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)

How the change has been tested

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Change checklist

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• My code follows the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests using ginkgo that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes