We want to test Simplicity activation using evbparams.

This will effectively activate Simplicity as soon as the sole Liquid
Testnet signer is updated.

Copy the parameters for mainnet because they seem to have worked fine
for Taproot and are therefore a good starting point for Simplicity.
Copy them for regtest so that we can also copy the functional test for
activation, without needing to change a whole bunch of numbers.