common: Make Shanghai the default hardfork

[g11tech]

Shift the default hf to Shanghai

(build on top of #2652 ), would be rebased once 2652 merges

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop-v7@2005528). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

Flag	Coverage Δ
block	90.57% <0.00%> (?)
blockchain	90.43% <0.00%> (?)
client	87.04% <0.00%> (?)
common	95.76% <0.00%> (?)
devp2p	91.61% <0.00%> (?)
ethash	∅ <0.00%> (?)
evm	79.35% <0.00%> (?)
rlp	∅ <0.00%> (?)
statemanager	88.08% <0.00%> (?)
trie	90.52% <0.00%> (?)
tx	95.45% <0.00%> (?)
util	81.50% <0.00%> (?)
vm	84.39% <0.00%> (?)

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

[gabrocheleau]

Lgtm

[holgerd77]

LGTM, thanks a lot, cool! 🙂 👍

Will directly merge in.