Add unlocking lock id to BeginUnlocking response (backport #4489)

[mergify]

This is an automatic backport of pull request #4489 done by Mergify.
Cherry-pick of d5f8210 has failed:

On branch mergify/bp/v15.x/pr-4489
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You are currently cherry-picking commit d5f8210a.
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Changes to be committed:
	modified:   CHANGELOG.md
	modified:   proto/osmosis/lockup/tx.proto
	modified:   x/lockup/keeper/iterator.go
	modified:   x/lockup/keeper/lock.go
	modified:   x/lockup/keeper/lock_test.go
	modified:   x/lockup/keeper/msg_server.go
	modified:   x/lockup/keeper/msg_server_test.go
	modified:   x/lockup/types/tx.pb.go
	modified:   x/superfluid/keeper/edge_case_test.go
	modified:   x/superfluid/keeper/unpool_test.go
	modified:   x/valset-pref/keeper_test.go
	modified:   x/valset-pref/types/expected_interfaces.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   x/superfluid/keeper/migrate_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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