[Move to ES Bridge] Build logstash-bridge and include in the plugin

[mashhurs]

Description

Creates gradle task to compile logstash-bridge module and add jar file to the plugin to make Stable API interfaces available.

FYI: CI failures which runs after gradle tasks are not related to this PR. The plugin is experiencing build issue against ES main now.

P.S: In between I changed the remote branch to move-to-es-bridge-api but since this doesn't harm anything, directly applying to main makes sense to me.

[mergify]

This pull request does not have a backport label. Could you fix it @mashhurs? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• If no backport is necessary, please add the backport-skip label

[andsel]

Left just a comment, if there is real reason to have the mustRunAfter please document why.

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 3a9222d

Failed CI Steps

• Unit test for 9.0.3, snapshot: false
• Integration test for 9.0.3, snapshot: false
• Unit test for 9.0.4-SNAPSHOT, snapshot: true
• Integration test for 9.0.4-SNAPSHOT, snapshot: true
• Unit test for 9.1.0-SNAPSHOT, snapshot: true
• Integration test for 9.1.0-SNAPSHOT, snapshot: true

History

• 💔 Build #585 failed e1e1d94
• 💔 Build #584 failed 061fdff
• 💚 Build #582 succeeded c8bfd21

[andsel]

LGTM

tested with

> ./gradlew localGem
> gem unpack logstash-filter-elastic_integration-9.2.0-java.gem
> jar tf ./vendor/jar-dependencies/co/elastic/logstash-filter-elastic_integration/9.2.0/logstash-filter-elastic_integration-9.2.0.jar  | grep logstashbridge

[mashhurs]

Plugin build issue is resolved, I have retried the CI jobs and they are 🟢 now.