fix: prevent signing from wrong key in multisig (backport #1319)

[mergify]

Description

closes: #XXXX

When signing an multisig tx, you are required to provide the multisig address (--multisig) and the key you are signing with (--from), but there's no check that the key is actually part of the multisig. This makes it very easy to accidentally sign with the wrong key and only figure it out when you try to broadcast the invalid tx that includes a signature from a key thats not in the multisig.

• backport fix: Prevent signing from wrong key in multisig cosmos/cosmos-sdk#12548

Motivation and context

How has this been tested?

Screenshots (if appropriate):

Checklist:

• I followed the contributing guidelines and code of conduct.
• I have added a relevant changelog to CHANGELOG.md
• I have added tests to cover my changes.
• I have updated the documentation accordingly.
• I have updated API documentation client/docs/swagger-ui/swagger.yaml

---

This is an automatic backport of pull request #1319 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of c051dcc has failed:

On branch mergify/bp/release/v0.48.x/pr-1319
Your branch is up to date with 'origin/release/v0.48.x'.

You are currently cherry-picking commit c051dcc91.
  (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:   x/auth/client/cli/tx_multisign.go
	modified:   x/auth/client/cli/tx_sign.go
	modified:   x/auth/client/testutil/suite.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md

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

[codecov]

Codecov Report

Attention: Patch coverage is 34.04255% with 31 lines in your changes are missing coverage. Please review.

Project coverage is 69.76%. Comparing base (1f8e902) to head (6e8c3a6).
Report is 10 commits behind head on release/v0.48.x.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           release/v0.48.x    #1324      +/-   ##
===================================================
- Coverage            69.78%   69.76%   -0.02%     
===================================================
  Files                  646      646              
  Lines                67507    67573      +66     
===================================================
+ Hits                 47109    47142      +33     
- Misses               18212    18242      +30     
- Partials              2186     2189       +3     

Files	Coverage Δ
x/auth/client/testutil/suite.go	96.94% <100.00%> (+0.03%)	⬆️
x/auth/client/cli/tx_multisign.go	0.00% <0.00%> (ø)
x/auth/client/cli/tx_sign.go	0.00% <0.00%> (ø)

... and 3 files with indirect coverage changes