feat: make checksum optional in upgrade validation (backport #16511)

[mergify]

This is an automatic backport of pull request #16511 done by Mergify.
Cherry-pick of 62709ad has failed:

On branch mergify/bp/release/v0.50.x/pr-16511
Your branch is up to date with 'origin/release/v0.50.x'.

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Changes to be committed:
	modified:   tools/cosmovisor/CHANGELOG.md
	modified:   tools/cosmovisor/README.md
	modified:   tools/cosmovisor/args.go
	modified:   tools/cosmovisor/args_test.go
	modified:   tools/cosmovisor/upgrade.go
	modified:   x/upgrade/CHANGELOG.md
	modified:   x/upgrade/client/cli/query.go
	modified:   x/upgrade/client/cli/tx.go
	modified:   x/upgrade/plan/downloader.go
	modified:   x/upgrade/plan/downloader_test.go
	modified:   x/upgrade/plan/info.go
	modified:   x/upgrade/plan/info_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   tools/cosmovisor/go.mod
	both modified:   tools/cosmovisor/go.sum

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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[julienrbrt]

Reverting all cosmovisor changes here, as cosmovisor changes do not need to be backported (tagged from main)