feat: update SDK to v0.43.0 and add upgrade handler

[akhilkumarpilli]

• Update cosmos SDK version to v0.43.0-rc2
• Add upgrade handler with name v0.43.0-upgrade

TODO: Need to test upgrade thoroughly and update upgrade handler if needed any changes.

[codecov]

Codecov Report

Merging #1262 (c136c5b) into master (3bbfe80) will decrease coverage by 4.12%.
The diff coverage is 47.50%.

❗ Current head c136c5b differs from pull request most recent head 550d8af. Consider uploading reports for the commit 550d8af to get more accurate results

@@            Coverage Diff             @@
##           master    #1262      +/-   ##
==========================================
- Coverage   77.88%   73.75%   -4.13%     
==========================================
  Files           6        6              
  Lines         529      583      +54     
==========================================
+ Hits          412      430      +18     
- Misses        112      145      +33     
- Partials        5        8       +3     

[github-actions]

Marked as stale; will be closed in five days.

Cut bait or go fishing!

[akhilkumarpilli]

Closing this PR as these changes are already implemented in #1343