Add pagination to GetValidatorSetByHeight response

[aleem1314]

Description

closes: #8560

---

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

[codecov]

Codecov Report

Merging #8567 (5a8028b) into master (e306e5b) will increase coverage by 0.00%.
The diff coverage is 44.44%.

@@           Coverage Diff           @@
##           master    #8567   +/-   ##
=======================================
  Coverage   61.43%   61.43%           
=======================================
  Files         656      656           
  Lines       37533    37535    +2     
=======================================
+ Hits        23059    23061    +2     
- Misses      12065    12067    +2     
+ Partials     2409     2407    -2     

Impacted Files	Coverage Δ
client/rpc/validators.go	0.00% <0.00%> (ø)
client/grpc/tmservice/service.go	68.42% <100.00%> (+2.96%)	⬆️
client/grpc_query.go	28.26% <0.00%> (-0.91%)	⬇️
baseapp/grpcserver.go	2.56% <0.00%> (-0.14%)	⬇️
server/grpc/server.go	62.50% <0.00%> (ø)
baseapp/grpcrouter.go	86.04% <0.00%> (+6.04%)	⬆️

[amaury1093]

ACK, could you add a test?