Double the block gas limits

This proposal increases the block gas limit to 120M, from the existing 60M.

We are currently frequently hitting block gas limits, even though the native execution times remain quite low. We see that we're frequently getting 10-20 trades per block, with block's nearing the gas limit. (Due to several affects, not just low gas limit, but the gas limit is still a part of it)

Furthermore, the bonding & unbonding of LP shares for yield farming still takes a lot of gas, even though its fixed in the subsequent chain software version. Bonding of LP shares is nearing 30M gas per tx (until the next upgrade). For unbonding it depends on how many locks its trying to unbond at once. (~25M each atm) Increasing the limit should improve UX, without notably increasing the block times. In the future, if we find that we're getting into execution time limits per block, we should start tuning per-tx gas parameters and optimizing the code to improve these speeds. The chain should absolutely be able to support 100+ trades per block, and we need our gas limits to be able to reflect this. I propose that only if the chain starts seeing too high of an execution time per block, and a software patch would take too long, do we start tuning down the block gas limit.