services/horizon/internal/ingest: Fix transaction processor metrics

[tamirms]

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

When horizon v2.27.0 was deployed to production the ingestion duration of the transaction processor appeared to decrease dramatically:

Unfortunately, this is not due to any performance improvements but rather a bug in our reporting of metrics to prometheus.

In the 2.27.0 release ingestion filtering was enabled by default. When filtering is enabled, Horizon will run an additional transaction processor on the history_transactions_filtered_tmp table. The transaction processor for the history_transactions_filtered_tmp table has the same type is the regular transaction processor. The type of a transaction is used as the label for the prometheus metric capturing ingestion run duration. So, the metric for the history_transactions_filtered_tmp processor was getting reported instead of the normal transactions processor because they both had the same label.

This PR aims to fix this bug and to prevent bugs like this from occurring again by ensuring that all ingestion processor metrics have unique label names.

Known limitations

[N/A]