refactor(x/ecocredit): improve basket denom validation

[ryanchristo]

Description

Closes: #1163 / Ref: #1162 (comment)

This pull request separates basket denom regex and custom coin regex and adds basket denom validation.

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[codecov]

Codecov Report

Merging #1200 (810a068) into master (d7c114c) will decrease coverage by 0.31%.
The diff coverage is 95.23%.

❗ Current head 810a068 differs from pull request most recent head a7116b6. Consider uploading reports for the commit a7116b6 to get more accurate results

@@            Coverage Diff             @@
##           master    #1200      +/-   ##
==========================================
- Coverage   70.35%   70.04%   -0.32%     
==========================================
  Files         234      235       +1     
  Lines       23575    24032     +457     
==========================================
+ Hits        16587    16834     +247     
- Misses       5569     5757     +188     
- Partials     1419     1441      +22     

Flag	Coverage Δ
experimental-codecov	70.07% <95.23%> (-0.34%)	⬇️
stable-codecov	64.80% <95.23%> (-0.22%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

[technicallyty]

lgtm