More configurable options for fee estimation

[diwakergupta]

Since Nakamoto launch, many builders (esp. defi apps), users, wallet providers have been observing high fee estimates from the /v2/fees/transaction endpoint.

It would be great if node operators could experiment with different parameters in the cost and fee estimation, to see what works well for them and their users. While there is some configurability today (as documented here), it's pretty limited:

Estimators and metrics can be selected using the configuration fields above, though the default values are the only options currently.

Specifically, some configurable parameters in WeightedMedianFeeRateEstimator and PessimisticEstimator might help.