Remove hardcoded chain parameters

https://gitlab.com/PBSA/peerplays/-/blob/develop/libraries/chain/db_maint.cpp#L2035

libraries/chain/db_maint.cpp contains hardcoded chain params in function void update_son_params(database& db).

The implementation does not control that these parameters are applied only once, immediately after HARDFORK_SON2_TIME, but it will continue to apply them on each maintenance block, which will prevent changes initiated through chain parameter change, or asset update proposal to apply.

Additionally, changing BTC asset properties is redundant, since the asset is already created with appropriate flags.

1. Remove changing BTC asset properties
2. Make sure that son count is changes only once, immediately after HARDFORK_SON2_TIME
3. Test both Mainnet and Testnet implementations