core metrics changes

[murali-partha]

Description

What does this PR do?

This PR introduces all the ce file changes that are being introduced as part of the Vault Operator Import feature on Vault Enterprise. This is the related Vault Enterprise PR This is as suggested in the instructions here.

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.

[hashicorp-cla-app[bot]]

All committers have signed the CLA.

[github-actions[bot]]

CI Results: All Go tests succeeded! :white_check_mark:

[github-actions[bot]]

Build Results: All builds succeeded! :white_check_mark:

[VioletHynes]

Approved, although merge conflicts must be resolved (i.e. resolve the go.mod conflicts on ent and then re-make this CE PR) before this can be merged