services/horizon: Fix claimable balance query

[urvisavla]

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

Explicitly qualify columns with table name/alias in claimable balance db query.

Query before the fix:
SELECT cb.id, cb.claimants, cb.asset, cb.amount, cb.sponsor, cb.last_modified_ledger, cb.flags FROM claimable_balances cb JOIN claimable_balance_claimants ON claimable_balance_claimants.id = cb.id WHERE (last_modified_ledger, id) > ($1, $2) AND claimable_balance_claimants.destination = $3 AND cb.asset = $4 ORDER BY last_modified_ledger ASC, id ASC LIMIT 200

With the fix:
SELECT cb.id, cb.claimants, cb.asset, cb.amount, cb.sponsor, cb.last_modified_ledger, cb.flags FROM claimable_balances cb JOIN claimable_balance_claimants ON claimable_balance_claimants.id = cb.id WHERE (cb.last_modified_ledger, cb.id) > ($1, $2) AND claimable_balance_claimants.destination = $3 AND cb.asset = $4 ORDER BY last_modified_ledger ASC, id ASC LIMIT 200

Why

Resolves Issue #5199

Issue #4907 introduced a join between claimable_balances and claimable_balance_claimants tables which resulted in unqualified columns in claimable balance query with cursor cursor causing database error column reference 'last_modified_ledger' is ambiguous.

Known limitations