tests: Add more dynamic fee tx tests

[MalteHerrmann]

Addresses: #1017

Description

Hi, I want to start contributing to the repo and figured writing tests is a good way to start.
Please point me towards any improvements I can make for future PRs and changes that are necessary for this PR to be accepted.

I have added a test for the AsEthereumData method of DynamicFeeTx and some edge case tests regarding overflowing big.Ints.

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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)

[fedekunze]

ACK, thanks!

[codecov]

Codecov Report

Merging #1032 (fc9430b) into main (ea3c16e) will increase coverage by 0.38%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1032      +/-   ##
==========================================
+ Coverage   59.32%   59.70%   +0.38%     
==========================================
  Files          80       80              
  Lines        6576     6576              
==========================================
+ Hits         3901     3926      +25     
+ Misses       2456     2434      -22     
+ Partials      219      216       -3     

Impacted Files	Coverage Δ
x/evm/types/dynamic_fee_tx.go	89.94% <0.00%> (+13.96%)	⬆️

[fedekunze]

@MalteHerrmann you can prob open a similar PR for x/evm/msg.go or x/evm/access_list_tx.go

[MalteHerrmann]

@fedekunze Will do!