governance: fetch delegation before governance proposal start epoch

[Fraccaman]

Describe your changes

Closes #3937

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes
• If this PR requires changes to the docs or specs, a corresponding PR is opened in the namada-docs repo
  • Relevant PR if applies:
• If this PR affects services such as namada-indexer or namada-masp-indexer, a corresponding PR is opened in that repo
  • Relevant PR if applies:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.21%. Comparing base (602d154) to head (54e5a45).
Report is 316 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4032   +/-   ##
=======================================
  Coverage   73.20%   73.21%           
=======================================
  Files         341      341           
  Lines      105151   105151           
=======================================
+ Hits        76978    76982    +4     
+ Misses      28173    28169    -4     

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[brentstone]

Can you add a test here? @Fraccaman @tzemanovic