abci: change client to use multi-reader mutexes (backport #6306)

[mergify]

This is an automatic backport of pull request #6306 done by Mergify.
Cherry-pick of 1c4dbe3 has failed:

On branch mergify/bp/v0.34.x/pr-6306
Your branch is up to date with 'origin/v0.34.x'.

You are currently cherry-picking commit 1c4dbe30d.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   abci/client/client.go
	modified:   abci/client/grpc_client.go
	modified:   abci/client/socket_client.go
	modified:   consensus/common_test.go
	modified:   consensus/reactor_test.go
	modified:   proxy/client.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   abci/client/local_client.go
	both modified:   consensus/byzantine_test.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[lgtm-com]

This pull request introduces 1 alert when merging 279f806 into 0c05841 - view on LGTM.com

new alerts:

• 1 for Unreachable statement

[tessr]

@tychoish can you resolve the conflicts here and then we can talk about doing another 0.34 release to get the changes out requested by Terra?

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (v0.34.x@0c05841). Click here to learn what that means.
The diff coverage is n/a.

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