Devnet 5 Legacy RPL Stake interface changes

[thomaspanf]

This PR adds support for interface updates targeting this commit: rocket-pool/rocketpool@898af10

• New file /v1.3.1/protocol/node.go for legacy bindings for commands being removed in Saturn: getMinimumPerMinipoolStake and getMaximumPerMinipoolStake.

• Bindings for the new calls getMinimumLegacyRPLStake and getNodeMinimumLegacyRPLStake

• Removed getNodeMaximumRPLStakeForMinipools from bindings, as it no longer exists in rp:1.4. Houston uses getNodeMaximumRPLStake to fetch the amount of RPL that a node can withdraw down to. The new command is called getNodeMinimumLegacyRPLStake.

• In previous versions of Rocket Pool, the field used to represent the amount of RPL that a node can withdraw down to was called MaximumRplStake. In Saturn, the same field is now called MinimumLegacyRPLStake. It's a bit confusing. The SN needs to support the Houston 1.3.1 interface on top of 1.4, so I've used the variable names RplStakeThreshold and RplStakeThresholdFraction across the SN to represent the amount of RPL that a node can withdraw down to.

• Added pdao command to propose the new setting node.minimum.legacy.staked.rpl.

• Updated get-settings api and cli to support the new settings.

• Wrapped the deprecated settings (node.per.minipool.stake.minimum and node.per.minipool.stake.maximum) inside a check to ensure they aren't accessible when saturn is deployed.

• Deleted unused code in node-status api: response.MinimumRplStake, response.PendingMinimumRplStake, response.PendingMaximumRplStake, response.MinimumRplStake.

• New information displayed in node status cli