Gray Glacier HF Support

[holgerd77]

In order to get a bit more time for the Merge a difficulty bomb delay has been decided on ACD 140 (June 10 2022).

There is an EIP out for that EIP-5133 but I am not 100% sure if this will be taken in 1:1 so this would need some confirmation, there is also work on some associated tests done here.

We should implement this to support this HF, implementation is pretty straight forward and can be followed I guess more or less 1:1 along how the ArrowGlacier HF has been implemented in #1527 by @jochem-brouwer.

This should be submitted to both v5-maintenance and master.

[holgerd77]

Additional note: I am also not 100% sure if this affects only mainnet or also some other PoW test network.

[jochem-brouwer]

FYI, Geth just released this Gray Glacier HF so we can assume that the numbers are ok

[holgerd77]

Here is another test PR: ethereum/tests#1043

[holgerd77]

Have assigned Scotty here.

[holgerd77]

Closed by #1988 and #1984