VAULT-38888 Add prefix vault to metric summary definitions

[roh-a]

Description

This PR fixes an issue where duplicate metrics for core_leadership_lost, core_step_down and leadership_setup_failed were being exposed on the /sys/metrics?format=prometheus endpoint.
Refer this escalation ticket.

The Problem
Currently, the endpoint returns two versions of these metrics:

core_leadership_lost_*: A statically registered metric that is always zero.

vault_core_leadership_lost_*: The correct metric, which is properly populated at runtime.

This duplication is caused by a previous fix (PR #27966) that pre-registered the metrics to ensure their consistent availability. However, that registration did not account for the service name prefix added to metrics (in this case - vault).

The Solution
This change resolves the issue by adding the vault prefix to the static metric registrations. This aligns the pre-registered keys with the runtime keys, effectively eliminating the redundant, zero-value metrics from the output.

TODO only if you're a HashiCorp employee

• Backport Labels: If this fix needs to be backported, use the appropriate backport/ label that matches the desired release branch. Note that in the CE repo, the latest release branch will look like backport/x.x.x, but older release branches will be backport/ent/x.x.x+ent.
  • LTS: If this fixes a critical security vulnerability or severity 1 bug, it will also need to be backported to the current LTS versions of Vault. To ensure this, use all available enterprise labels.
• 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
  files.
• Jira: If this change has an associated Jira, it's referenced either
  in the PR description, commit message, or branch name.
• RFC: If this change has an associated RFC, please link it in the description.
• ENT PR: If this change has an associated ENT PR, please link it in the
  description. Also, make sure the changelog is in this PR, not in your ENT PR.

PCI review checklist

• I have documented a clear reason for, and description of, the change I am making.
• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.
• If applicable, I've documented the impact of any changes to security controls.

Examples of changes to security controls include using new access control methods, adding or removing logging pipelines, etc.

[hashicorp-cla-app]

All committers have signed the CLA.

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Project	Deployment	Preview	Comments	Updated (UTC)
vault-ui	Ready	Preview	Comment	Aug 19, 2025 5:52am

[github-actions]

CI Results:
All Go tests succeeded! ✅

[stuti-sr]

I have provided a comment related to consistency of name in code base

[stuti-sr]

Instead of hardcoding metric name arrays at multiple places, we should define them as constants/variables and reuse them.
var (
metricCoreStepDown = []string{"vault","core", "step_down"}
metricCoreLeadershipLost = []string{"vault","core", "leadership_lost"}
metricCoreLeadershipSetupFailed = []string{"vault","core", "leadership_setup_failed"}
)

Instead of using hard coded value: metrics.MeasureSince([]string{"core", "step_down"}, time.Now())
use metrics.MeasureSince(metricCoreStepDown, startTime)
similarly should also update:
line 314, 586 , 595, 659, 684, 696, 716, 753

This will help with maintainability, reduces duplication, and ensures metric names stay consistent across the codebase.

[github-actions]

Build Results:
All builds succeeded! ✅

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

Copy workflow completed!

From	To	Error
hashicorp/vault#2743677675	hashicorp/vault-enterprise#2758925202