Problem: base fee conversion could panic on overflow (backport #433)

[mmsqe]

• prevent integer overflow

use sdkmath.MaxBitLen

cleanup

• changelog

---

Closes: #XXX

Description

---

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

---

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

Attention: Patch coverage is 73.68421% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 63.39%. Comparing base (426480e) to head (9ecd146).

❗ Current head 9ecd146 differs from pull request most recent head 095395c. Consider uploading reports for the commit 095395c to get more accurate results

Additional details and impacted files

@@                    Coverage Diff                     @@
##           release/v0.21.x-cronos     #435      +/-   ##
==========================================================
+ Coverage                   63.36%   63.39%   +0.02%     
==========================================================
  Files                         129      129              
  Lines                       12252    12269      +17     
==========================================================
+ Hits                         7764     7778      +14     
- Misses                       3985     3988       +3     
  Partials                      503      503              

Files	Coverage Δ
x/feemarket/keeper/params.go	65.00% <100.00%> (ø)
types/int.go	55.88% <72.22%> (+26.47%)	⬆️