Description and Motivation

This PR fixes some mempool processing issues for the Injective bockchain: decimal handling and "ethereum signed messages" handling.

Related Issues

[x] I have read Migaloo's contribution guidelines.
[x] My pull request has a sound title and description (not something vague like Update index.md)
[x] All existing and new tests are passing (if any).
[x] I updated/added relevant documentation.
[x] The code is formatted properly using eslint