Backport of api/seal-status: fix deadlock when namespace is set on seal-status calls into release/1.15.x

[hc-github-team-secure-vault-core]

Backport

This PR is auto-generated from #23861 to be assessed for backporting due to the inclusion of the label backport/1.15.x.

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The person who merged in the original PR is:
@jasonodonnell
This person should manually cherry-pick the original PR into a new backport PR,
and close this one when the manual backport PR is merged in.

merge conflict error: POST https://api.github.com/repos/hashicorp/vault/merges: 409 Merge conflict []

The below text is copied from the body of the original PR.

---

PR #10725 introduced a change to support namespaces in vault status requests but introduced a deadlock on calls to sys/seal-status when namespaces are included.

When requests have a namespace configured the handler routes the request through switchedLockHandleRequest and holds the read statelock for the duration of the request:

vault/vault/request_handling.go

Lines 530 to 533 in 550c99a

	if doLocking {
	c.stateLock.RLock()
	defer c.stateLock.RUnlock()
	}

.

I've added a locking arg so the caller can decide if the statelock needs to be grabbed or not.

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