exp/tools/dump-ledger-state: Fix dump ledger state script

[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

Fixes #3022

Stellar Core recently modified its database schema which consequently broke the SQL queries used in dump_core_db.sh.
This commit fixes the SQL queries so that it works with the latest version of Stellar Core.
This commit also adds support for claimable balances which were introduced in Protocol 14/15.

Stellar Core's schema is documented here: https://github.com/stellar/stellar-core/blob/master/docs/db-schema.md .