Close #27023: Add capability to override telemetry URL using local properties

[rocketsroger]

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features. In addition, it includes a screenshot of a successful accessibility scan to ensure no new defects are added to the product.

QA

• QA Needed

To download an APK when reviewing a PR (after all CI tasks finished running):

1. Click on Checks at the top of the PR page.
2. Click on the firefoxci-taskcluster group on the left to expand all tasks.
3. Click on the build-debug task.
4. Click on View task in Taskcluster in the new DETAILS section.
5. The APK links should be on the right side of the screen, named for each CPU architecture.

GitHub Automation

Fixes #27023

[jonalmeida]

local.properties > pref > default?

Let's document this on the README in the localproperties helpers or somewhere else in our docs/ dir (but not wiki).

It's easy to make the mistake that a value is set in local.properties and then try to set a pref value that is not actually used even though it's saved. I'm not sure how you'd like to handle that, so I'll leave it to you to consider and not block this PR for now.

[rocketsroger]

local.properties > pref > default?

Let's document this on the README in the localproperties helpers or somewhere else in our docs/ dir (but not wiki).

Sounds good I'll document this in the README.

It's easy to make the mistake that a value is set in local.properties and then try to set a pref value that is not actually used even though it's saved. I'm not sure how you'd like to handle that, so I'll leave it to you to consider and not block this PR for now.

Yes, this is a bit awkward. Let me think if there's a simple way to avoid this. Thanks

[jonalmeida]

The updated changes look good to me too, thanks!