chore: improve ES Check type inference

[kylezs]

Pull Request

Checklist

Please conduct a thorough self-review before opening the PR.

• I am confident that the code works.
• I have written sufficient tests.
• I have written and tested required migrations.
• I have updated documentation where appropriate.

Summary

I hit an issue when writing a check like so on my PR:

number_of_open_elections_is(_pre, post, n: ElectionCount) {
	assert_eq!(post.unsynchronised_state.open_elections, n, "Number of open elections should be {}", n);
},

and it was because without explicitly comparing the whole post-state as is currently done on some Checks, it can't infer the rest of the state. Fixing this by explicitly providing the type in the closure, writing checks should remain just as clean.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72%. Comparing base (277b152) to head (f3eee8d).
Report is 7 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #5448    +/-   ##
======================================
- Coverage     72%     72%    -0%     
======================================
  Files        490     490            
  Lines      87053   86929   -124     
  Branches   87053   86929   -124     
======================================
- Hits       62423   62242   -181     
- Misses     21675   21729    +54     
- Partials    2955    2958     +3     

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