Add min-fee param for the batch relayer

[dzmitryhil]

Add and start checking for the batch min-fee pararm on the orchsestrator/relayer side.

• The param is a param of the gbt config toml file.
• This param should be optional - if not provided we accept all batches
• And example of the param is: 100anom,20stake. Means we should support a list of fees. This state is possible because we allow fee denom change, so to forse it we should implement it this way.
• If the total fee of a batch < min-fee the batch should be skipped.
• It is better to filter the batches on the cosmos rather then on the relayer side.

This issue can be done from the "native-reward" base branch.