feat: Allow connecting from the Notification Controller to the Repo Server without TLS (#19629)

[m-wynn]

Unsure if this should be a fix or a feature, so I created an enhancement proposal https://github.com/argoproj/argo-cd/issues/19629.

All of the Argo CD components I have worked with have a way to disable TLS between each other via the argocd-cmd-params-cm ConfigMap. One issue I've run into is, when calling .repo.GetCommitMetadata in notifications templates, it tries to reach out to the Repo Server over TLS. There does not seem to be an easy way to disable it, short of overlaying the notifications template deployment itself and adding a command line flag.

This is necessary for environments where Istio is managing mutual TLS between each component (https://github.com/argoproj/argo-cd/issues/2784).

Closes #19629

Checklist:

• [x] Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• [x] The title of the PR states what changed and the related issues number (used for the release note).
• [x] The title of the PR conforms to the Toolchain Guide
• [x] I've included "Closes [ISSUE #]" or "Fixes [ISSUE #]" in the description to automatically close the associated issue.
• [ ] I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• [ ] Does this PR require documentation updates?
• [x] I've updated documentation as required by this PR.
• [x] I have signed off all my commits as required by DCO
• [ ] I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• [ ] My build is green (troubleshooting builds).
• [x] My new feature complies with the feature status guidelines.
• [x] I have added a brief description of why this PR is necessary and/or what this PR solves.
• [ ] Optional. My organization is added to USERS.md.
• [ ] Optional. For bug fixes, I've indicated what older releases this fix should be cherry-picked into (this may or may not happen depending on risk/complexity).