Move some Param types from Keeper to Types in staking

[jgimeno]

Description

I realized while trying to make gaia work that for some reason those types were in keeper package instead of types, it was the only one, so I moved it to be consistent.

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Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[codecov]

Codecov Report

Merging #6451 into master will decrease coverage by 0.00%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #6451      +/-   ##
==========================================
- Coverage   55.74%   55.74%   -0.01%     
==========================================
  Files         466      466              
  Lines       27890    27890              
==========================================
- Hits        15548    15546       -2     
- Misses      11229    11231       +2     
  Partials     1113     1113              

[alexanderbez]

ACK