Fix service loader for jdk21

[mswintermeyer]

Before this PR

Previous attempt at adding support for jdk21 didn't work, because the service loader config wasn't correct.

After this PR

Fixes jdk21 support, and now uses integration tests rather than unit tests for the project so we actually test jdk21 functionality appropriately.
==COMMIT_MSG==
Jdk21 support (round 2)
==COMMIT_MSG==

Possible downsides?

[changelog-app]

Generate changelog in changelog/@unreleased

What do the change types mean?

• feature: A new feature of the service.
• improvement: An incremental improvement in the functionality or operation of the service.
• fix: Remedies the incorrect behaviour of a component of the service in a backwards-compatible way.
• break: Has the potential to break consumers of this service's API, inclusive of both Palantir services
  and external consumers of the service's API (e.g. customer-written software or integrations).
• deprecation: Advertises the intention to remove service functionality without any change to the
  operation of the service itself.
• manualTask: Requires the possibility of manual intervention (running a script, eyeballing configuration,
  performing database surgery, ...) at the time of upgrade for it to succeed.
• migration: A fully automatic upgrade migration task with no engineer input required.

Note: only one type should be chosen.

How are new versions calculated?

• ❗The break and manual task changelog types will result in a major release!
• 🐛 The fix changelog type will result in a minor release in most cases, and a patch release version for patch branches. This behaviour is configurable in autorelease.
• ✨ All others will result in a minor version release.

Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

Jdk21 support (round 2)

Check the box to generate changelog(s)

• Generate changelog entry

[svc-autorelease]

Released 1.11.0