UI: Fix token renewal breaking policy checks

[hellobontempo]

Description

The UI makes a lot of inferences based on the shape of the auth response we receive. The UI relies on the namespace_path from the auth response to set the user's root namespace which is then used to calculate capabilities.

vault/ui/app/adapters/capabilities.js

Lines 16 to 30 in dcdbacd

	/*
	users don't always have access to the capabilities-self endpoint in the current namespace,
	this can happen when logging in to a namespace and then navigating to a child namespace.
	adding "relativeNamespace" to the path and/or "this.namespaceService.userRootNamespace"
	to the request header ensures we are querying capabilities-self in the user's root namespace,
	which is where they are most likely to have their policy/permissions.
	*/
	_formatPath(path) {
	const { relativeNamespace } = this.namespaceService;
	if (!relativeNamespace) {
	return path;
	}
	// ensure original path doesn't have leading slash
	return `${relativeNamespace}/${sanitizeStart(path)}`;
	}

renew-self does not return namespace_path, so this PR manually adds it in the renew() method, if it exists. The auth code is challenging to parse and is prone to regressions. I double checked that this change does not affect the bug the previous PR was solving that introduced these code changes: https://github.com/hashicorp/vault/pull/24168/files

TODO only if you're a HashiCorp employee

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• ENT Breakage: If this PR either 1) removes a public function OR 2) changes the signature
  of a public function, even if that change is in a CE file, double check that
  applying the patch for this PR to the ENT repo and running tests doesn't
  break any tests. Sometimes ENT only tests rely on public functions in CE
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Build Results:
All builds succeeded! ✅

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CI Results:
All Go tests succeeded! ✅

[Monkeychip]

really solid logic writing here!

[Monkeychip]

The logic here seems solid (and easy to read, thank you). Ping when you're ready for final review.