ingest: Use a *random* history archive from the Captive Core configuration list

[Shaptic]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with name of package that is most changed in the PR, ex.
  services/friendbot, or all or doc if the changes are broad or impact many
  packages.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.
• I've updated any docs (developer docs, .md
  files, etc... affected by this change). Take a look in the docs folder for a given service,
  like this one.

Release planning

• I've updated the relevant CHANGELOG (here for Horizon) if
  needed with deprecations, added features, breaking changes, and DB schema changes.
• I've decided if this PR requires a new major/minor version according to
  semver, or if it's mainly a patch change. The PR is targeted at the next
  release branch if it's not a patch change.

What

Introduces historyarchive.ConnectAny, which chooses a random history archive from a list of URLs until succeeding.

Why

Previously, listing more than one history archive in the Captive Core configuration had no impact since the first was always used. This is (more or less) a preliminary effort into being smarter about the way we use history archives.

Moving forward, the goal may be to refactor the historyarchive library to use a random archive for every request for redundancy purposes, but this can be done in future PRs.

Known limitations

I'd like to add a test.

[Shaptic]

Closing in lieu of #3402.