Clean up 11-beefy, make it more idiomatic golang #7

[thomasmodeneis]

Description

This PR tries to cleanup the code so that we have more idiomatic go files and related tests. Bellow you will find the more complete explanation for each one of the sections.

Update beefy.proto

• Remove not used libs
• Add comment to BeefyMmrLeaf to fix make proto cmd issue

Idiomatic Golang related

• Update method receivers var name on so that they are all the same for all methods. Files changed: beefy.pb.go
• Update test cases to make use of require.NoError, require.Equal, require.NotEmpty,
• Update fmt.Printf to t.Logf or related compatible log func for tests.
• Remove not require castings
• Update error messages to not start with capital letter
• Update other method signatures such as fetchParaIds to fetchParaIDs to follow go convention for Initialisms

Fixed typos

absense -> absence

Update go.mod

• Gossamer to latest

closes: #7

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• [ ] Targeted PR against correct branch (see CONTRIBUTING.md)
• [ ] Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• [ ] Code follows the module structure standards.
• [ ] Wrote unit and integration tests
• [ ] Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• [ ] Added relevant godoc comments.
• [ ] Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• [ ] Re-reviewed Files changed in the Github PR explorer
• [ ] Review Codecov Report in the comment section below once CI passes