deduplicate gas estimation code

[altergui]

these 5 funcs do some kind of gas estimation

func (tm *TxManager) EstimateGas(
func (tm *TxManager) BuildDynamicFeeTx(
func (tm *TxManager) rebuildRegularTx(
func (tm *TxManager) rebuildBlobTx(
func (tm *TxManager) cancelTx(ctx context.Context, ptx *PendingTransaction) error {

we should really dedup all that code (maybe convert rebuildRegularTx into a buildRegularTx that is reused?)

and maintain a single method that correctly estimates gas for any passed tx (with blobs or without, etc), and use that method (and only that one) among all of the codebase

so git grep tm.cli.SuggestGasTipCap , tm.cli.SuggestGasPrice and tm.cli.EstimateGas should yield only 1 match

[altergui]

it might make sense to do this in #246