Fix tradeagg rebuild from reingest command with parallel workers

[sreuland]

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

for reingest command, consolidate the invocations of rebuilding of trade agg buckets to once at end of all parallel workers

Why

this avoids getting:

Error rebuilding trade aggregations: could not rebuild trade aggregation bucket: exec failed: pq: duplicate key value violates unique constraint \"history_trades_60000_pkey\

at the end of a parallel worker's range ingestion

Closes #5127

Known limitations

this is targeting the 2.28.0 release branch, it will be ported to master as part of porting the final release back to master later.

[urvisavla]

Reingestion logic has some intricacies but the changes lgtm.