!fix(erc712): support MsgCreateValidator

[ramacarlucho]

Closes: #XXX

Description

The eip712 was missing some types necessary for the createValidator msg.
Added tests for several msgs for eip712.

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For contributor use:

• 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

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For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
• Reviewers assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #1346 (406053a) into main (5c80a55) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1346      +/-   ##
==========================================
- Coverage   54.79%   54.77%   -0.03%     
==========================================
  Files         107      107              
  Lines        9990     9994       +4     
==========================================
  Hits         5474     5474              
- Misses       4245     4249       +4     
  Partials      271      271              

Impacted Files	Coverage Δ
ethereum/eip712/eip712.go	0.00% <0.00%> (ø)

[fedekunze]

ACK, can you add a changelog entry?