Implement eth_gasPrice

[austinabell]

Are we mapping gas cost to the ethermint equivalent of photons?

[austinabell]

Will just be using node's set gas price

[austinabell]

There is no historical gas price oracle within tendermint and if the value is being pulled from the min gas price from node's validator the config is multi-denom and is not available through the Tendermint RPC client (unless I'm missing a detail).

[github-actions]

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[freddyli7]

eth_gasPrice rpc endpoint has been added in #588, but it always returns 0, currently there is no gas price oracle so that we use default gas price in the code if user doesnt provide it.