feat: Support the gas estimator interface as part of CIP 18

[cmwaters]

Implementation ideas

This is a tracking issue for the celestia-node component of the gas estimator interface as outlined in CIP-18. Specifically, this constitutes implementing the client side, which will use the service for gas estimation and gas price estimation as part of the Blob Service.

Some noteworthy points:

• Light (and full) nodes will use the consensus node as the default server for requesting an estimation of the gas and the gas price. A user can optionally specify a different source for obtaining these values.
• Transactions that are purely PFBs can use the offline "modelled" way of measuring the gas and thus don't need to request from the server.
• [Optional] We may want to come up with some lazy way of requesting the price. i.e. in non-congested times, the price becomes quite predictable and thus we may not need to request a new price every time. Instead we can react to when a transaction fails CheckTx and update our local view of the minimum gas price.