login/mfa: update loginmfa cache and tests

[mickael-hc]

Description

normalizes the loginmfa totp code and adjusts the used code cache duration

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.
• 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.

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

[github-actions]

CI Results:
All Go tests succeeded! ✅

[github-actions]

Build Results:
All builds succeeded! ✅