Fix GetValidators status param

[anilcse]

Description

QueryValidators require status filter for gRPC queries and is a mandatory param. It's bit odd UX. As discussed with @amaurymartiny and @clevinson , changing status query param to optional and returning all the validators when there's no status supplied, seems to be a better solution. This PR addresses the same.

ref: #7019 (comment)

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• 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
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #7167 into master will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #7167      +/-   ##
==========================================
- Coverage   54.53%   54.53%   -0.01%     
==========================================
  Files         566      566              
  Lines       38729    38727       -2     
==========================================
- Hits        21121    21119       -2     
  Misses      15884    15884              
  Partials     1724     1724              

[clevinson]

lgtm. Thanks @anilcse !