fix: false-positive Stackdriver error in diagnose

[rnubel]

Description

Fixes the bug in operator diagnose as described in #31615.

operator diagnose contains checks to validate your Telemetry configuration. However, due to a glitch in how the coalesce helper handles booleans, it always reports an error with missing Stackdriver configuration if you omit Stackdriver settings (even if you specify other telemetry backend values correctly).

This change simply pulls the boolean out of the coalesce call and checks it separately. An updated unit test is included to validate a dogstatsd-only configuration.

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.
  • 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.
• 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.

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.

[hashicorp-cla-app]

Thank you for your submission! We require that all contributors sign our Contributor License Agreement ("CLA") before we can accept the contribution. Read and sign the agreement

Learn more about why HashiCorp requires a CLA and what the CLA includes

_{Have you signed the CLA already but the status is still pending? Recheck it.}

[vercel]

@rnubel is attempting to deploy a commit to the HashiCorp Team on Vercel.

A member of the Team first needs to authorize it.