feat: Add support for non-native tokens as txn fees

[ameten]

Issue

Scraper fails to store a transaction to database if the transaction has fees expressed in a non-native token.

Introduction

Currently if transaction fees are expressed in a non-native token, Scraper won't store it into database since it is not capable to calculate gas price in this case.

Tasks

1. Analyse how we would like to express gas price (in native token per unit, in non-native token per unit).
2. Analyse where we shall get mapping from non-native token id (ibc/<id>) to the name of this token.
3. Analyse where we shall get the conversion rate for gas price.
4. Analyse how we are going to store non-native token names (symbols) in Scraper database