internal/integration: use apply-load tooling from loadtest package in go-stellar-sdk

[cjonas9]

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 reviewed the changes in this PR and if I consider them worthwhile for being mentioned on release notes then I have updated the relevant CHANGELOG.md within the component folder structure. For example, if I changed horizon, then I updated (CHANGELOG.md. I add a new line item describing the change and reference to this PR. If I don't update a CHANGELOG, I acknowledge this PR's change may not be mentioned in future release notes.
• 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

Removes apply-load tooling from *_test.go file local to Horizon and uses similar tooling migrated to the SDK (see go-stellar-sdk/5940.

Why

We are currently adding an ingestion test in stellar-rpc that uses stellar-core's apply-load tooling. As such, the infrastructure previously built out in generate_ledgers_test.go has been moved to the SDK so it can be used by both repos. See stellar-rpc/711.

Known limitations

N/A

[Copilot]

Pull request overview

This PR updates Horizon’s integration-ledger generator test to stop maintaining a local copy of the stellar-core apply-load orchestration logic and instead use the equivalent apply-load tooling that has been migrated into go-stellar-sdk (via ingest/loadtest). This aligns Horizon with the shared approach needed by other repos (e.g., stellar-rpc) that also need to generate ledgers/fixtures from apply-load.

Changes:

• Replaced the large, Horizon-local apply-load runner + ledger/fixture streaming/verification helpers with loadtest.NewApplyLoad(...).RunApplyLoadAndWrite(...).
• Upgraded github.com/stellar/go-stellar-sdk (and go-xdr) to pick up the new ingest/loadtest package.
• Marked now-unused direct deps (e.g., toml, klauspost/compress) as indirect in go.mod.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
internal/integration/generate_ledgers_test.go	Switches the test from Horizon-owned apply-load helper code to the SDK’s ingest/loadtest implementation.
go.mod	Bumps go-stellar-sdk/go-xdr versions and adjusts dependency directness.
go.sum	Updates sums to match the new module versions.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.