chore: add Heap analytics

[peterbarnett03]

This is re-enabling some UX analytics software so we can better understand usage patterns for future UI/UX updates across the InfluxData suite of products.

Checklist

Authors and Reviewer(s), please verify the following:

• A PR description, regardless of the triviality of this change, that communicates the value of this PR
• Well-formatted conventional commit messages that provide context into the change
• Documentation updated or issue created (provide link to issue/PR)
• Signed CLA (if not already signed)
• Feature flagged, if applicable

[blegesse-w]

Hi @peterbarnett03, I'll prioritize this and take a look at it today. In the meantime, do you know why the monitor-ci job is failing? Haven't had a chance to investigate

[wdoconnell]

I'll pick this one up as part of the internal ticket we have for this. I think the CI failure is related to the mon ci runner changes we made recently so I can take a look. 👍

[wdoconnell]

@blegesse-w @peterbarnett03 This should be ready for a re-review. I added a few things here to what Pete already included:

1. Moved the heap identifiers to a ConfigCat int flag so that they stay out of code, and so we can control the staging/production identifiers through ConfigCat.
2. Cleans up the window object and script tags if the script fails.
3. Added some explanatory comments where necessary.

Overall I didn't see any regressions in behavior when I tested it local. This is less temperamental than the VWO script and the fetched scripts don't appear to interfere with page styles.

[peterbarnett03]

LGTM -- appreciate you moving the ID to a dynamic flag.