Add a method to osmoutils for having a function write to state if no err

[ValarDragon]

@antstalepresh made a neat method for doing this in a few places in the
superfluid epoch logic. This just refactors it to a standalone method in
osmoutils.

Furthermore, this PR also renames osmotestutils -> osmoutils, which
is a change I've wanted to make for a while.

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For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[codecov-commenter]

Codecov Report

Merging #872 (0e268a8) into main (9b977f3) will increase coverage by 0.41%.
The diff coverage is 69.23%.

@@            Coverage Diff             @@
##             main     #872      +/-   ##
==========================================
+ Coverage   19.89%   20.30%   +0.41%     
==========================================
  Files         191      191              
  Lines       24777    24772       -5     
==========================================
+ Hits         4929     5031     +102     
+ Misses      18984    18818     -166     
- Partials      864      923      +59     

Impacted Files	Coverage Δ
x/pool-incentives/client/cli/tx.go	0.00% <0.00%> (ø)
x/superfluid/keeper/distribution.go	85.71% <100.00%> (+12.03%)	⬆️
x/gamm/pool-models/balancer/balancerPool.pb.go	14.73% <0.00%> (+14.18%)	⬆️

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[UnityChaos]