Improvements to LoadSupport

[lbwexler]

Still very much a WIP based on convos with Greg and Lee

Thinking about whether as part of this we want to allow passing loadSpec explicitly to ExceptionHandlerOptions.

Might make it easier for implementations to just pass the loadSpec and know that Hoist will make the right decision about showing the alert (e.g. not for obsolete, auto-refresh)

Hoist P/R Checklist

Pull request authors: Review and check off the below. Items that do not apply can also be
checked off to indicate they have been considered. If unclear if a step is relevant, please leave
unchecked and note in comments.

• Caught up with develop branch as of last change.
• Added CHANGELOG entry, or determined not required.
• Reviewed for breaking changes, added breaking-change label + CHANGELOG if so.
• Updated doc comments / prop-types, or determined not required.
• Reviewed and tested on Mobile, or determined not required.
• Created Toolbox branch / PR, or determined not required.

If your change is still a WIP, please use the "Create draft pull request" option in the split
button below to indicate it is not ready yet for a final review.

Pull request reviewers: when merging this P/R, please consider using a squash commit to
collapse multiple intermediate commits into a single commit representing the overall feature
change. This helps keep the commit log clean and easy to scan across releases. PRs containing a
single commit should be rebased when possible.

[lbwexler]

This has been superceded by #4361