Common: Unify and Refactor set-/getHardforkByBlockNumber

[holgerd77]

Partly solves #2774

This PR does the following:

• Common.getHardforkByBlockNumber() -> Common.getHardforkBy() (+ strict bigint types)
• Common.setHardforkByBlockNumber() -> Common.setHardforkBy() (+ strict bigint types) 
• Blockchain.checkAndTransitionHardForkByNumber() BigIntLike -> strict bigint types 

[codecov]

Codecov Report

Merging #2798 (d214934) into master (2fd4087) will decrease coverage by 0.01%.
The diff coverage is 81.91%.

Additional details and impacted files

Flag	Coverage Δ
block	89.60% <100.00%> (+0.02%)	⬆️
blockchain	92.85% <100.00%> (+0.01%)	⬆️
client	87.09% <77.35%> (+0.01%)	⬆️
common	97.09% <100.00%> (-0.02%)	⬇️
devp2p	86.58% <ø> (ø)
ethash	∅ <ø> (∅)
evm	66.60% <ø> (ø)
rlp	∅ <ø> (∅)
statemanager	86.35% <ø> (ø)
trie	89.70% <ø> (-0.29%)	⬇️
tx	95.87% <ø> (ø)
util	85.31% <ø> (ø)
vm	77.55% <0.00%> (ø)

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[acolytec3]

Not approving yet as I'm reviewing this on mobile and CI is still running so want to take a second look later this morning but this looks great so far! Much more commonsense approach so far.

[acolytec3]

A great first start on reducing confusion on how we do this!