Set Prague as default HF

[jochem-brouwer]

This PR:

• Adds known fork timestamps for Holesky and Sepolia for Prague
• Adds dummy Prague fork (with dummy timestamp) for mainnet
• Sets default HFs to Prague for these chains

WIP, not sure when to merge, do we want to set Prague as default HF even if mainnet is not yet forked? 🤔

Closes #3876

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.62%. Comparing base (8630cc8) to head (29c5964).

Additional details and impacted files

Flag	Coverage Δ
block	77.03% <ø> (+0.16%)	⬆️
blockchain	85.69% <ø> (ø)
client	?
common	90.80% <100.00%> (+0.06%)	⬆️
devp2p	76.27% <ø> (ø)
ethash	81.04% <ø> (ø)
evm	71.17% <ø> (+0.12%)	⬆️
genesis	99.84% <ø> (ø)
mpt	59.52% <ø> (-0.21%)	⬇️
rlp	69.70% <ø> (ø)
statemanager	70.47% <ø> (ø)
tx	81.28% <ø> (+0.32%)	⬆️
util	85.54% <ø> (ø)
vm	58.62% <ø> (+0.81%)	⬆️
wallet	83.78% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

[jochem-brouwer]

Oh wait, I just realized the client will obviously switch to the correct hardfork even if mainnet is currently not forked to Prague yet.

I think mainnet timestamps will be choosen soon.

Note: Holesky will fork today :)

I suggest to merge this once mainnet timestamps are choosen and committed to this PR.

[holgerd77]

I suggest to merge this once mainnet timestamps are choosen and committed to this PR.

Yes, would agree