x/gov: gRPC query Service

[atheeshp]

Description

ref: #5921

---

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 #6491 into master will increase coverage by 0.08%.
The diff coverage is 80.15%.

@@            Coverage Diff             @@
##           master    #6491      +/-   ##
==========================================
+ Coverage   59.85%   59.94%   +0.08%     
==========================================
  Files         512      513       +1     
  Lines       31303    31434     +131     
==========================================
+ Hits        18737    18842     +105     
- Misses      11143    11156      +13     
- Partials     1423     1436      +13     

[lgtm-com]

This pull request introduces 3 alerts when merging 85811e1 into 67d079e - view on LGTM.com

new alerts:

• 3 for Useless assignment to local variable

[amaury1093]

lgtm 👍! I propose to keep the old comments on the struct fields.

addressed