count all refunds if more than one scr exists

[sstanculeanu]

Reasoning behind the pull request

• if more than one refund scrs are generated for a tx, only one is considered while computing the fee field on node api

Proposed changes

• take into account all refund scrs for node api

Testing procedure

• with feat branch, send a tx that generate multiple refunds

Pre-requisites

Based on the Contributing Guidelines the PR author and the reviewers must check the following requirements are met:

• was the PR targeted to the correct branch?
• if this is a larger feature that probably needs more than one PR, is there a feat branch created?
• if this is a feat branch merging, do all satellite projects have a proper tag inside go.mod?