feat: deprecate x/params usage in x/slashing

[likhita-809]

Description

Closes: #12288

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Author Checklist

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• confirmed the correct type prefix in the PR title
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[alexanderbez]

🙌

[alexanderbez]

@likhita-809 please add a changelog entry and we can merge this 👍

[codecov]

Codecov Report

Merging #12399 (12cfd15) into main (e7f78b4) will decrease coverage by 0.07%.
The diff coverage is 46.42%.

@@            Coverage Diff             @@
##             main   #12399      +/-   ##
==========================================
- Coverage   65.67%   65.59%   -0.08%     
==========================================
  Files         695      685      -10     
  Lines       72416    71635     -781     
==========================================
- Hits        47559    46990     -569     
+ Misses      22177    21999     -178     
+ Partials     2680     2646      -34     

Impacted Files	Coverage Δ
x/slashing/types/keys.go	0.00% <ø> (ø)
x/slashing/types/msg.go	23.33% <0.00%> (-17.85%)	⬇️
x/slashing/types/params.go	0.00% <0.00%> (ø)
x/slashing/types/params_legacy.go	0.00% <0.00%> (ø)
x/slashing/keeper/migrations.go	33.33% <50.00%> (-16.67%)	⬇️
x/slashing/module.go	66.30% <54.54%> (-3.02%)	⬇️
x/slashing/types/codec.go	63.15% <66.66%> (+0.65%)	⬆️
x/slashing/migrations/v2/migrate.go	72.72% <72.72%> (ø)
x/slashing/keeper/params.go	84.37% <80.95%> (-3.63%)	⬇️
x/slashing/keeper/keeper.go	46.15% <100.00%> (ø)
... and 14 more