[Task] Establish the shenyu-plugin-store build, test, E2E, and release baseline #7294

Background

apache/shenyu-plugin-store is the target repository for optional ShenYu plugins, but its current master branch is not yet a reliable migration target:

• it has no Maven wrapper even though the PR template requires ./mvnw clean install;
• it has no GitHub Actions workflow;
• a clean root build fails because nested aggregator POMs resolve shenyu-plugin-store through the wrong relative path;
• shenyu-plugin-tars explicitly skips Surefire tests;
• plugin code is coupled to classes that may be removed from apache/shenyu (Motan already references removed enum/DTO members);
• artifact publication ownership and the supported ShenYu compatibility range are not documented.

This issue is the blocking foundation for all plugin-by-plugin migrations.

Scope

Repository build contract

• Add and commit Maven Wrapper files.
• Fix aggregator parent resolution so a clean checkout builds from the repository root.
• Separate the plugin-store release version from the consumed ShenYu core/API version.
• Import or depend on a released ShenYu BOM/API contract without relying on an unpublished reactor.
• Run Checkstyle, Apache RAT, compilation, unit tests, and packaging from one documented command.
• Remove all module-level test skips unless a documented profile isolates an external integration test.

CI and compatibility

• Add GitHub Actions for JDK 17 build/test/RAT/checkstyle.
• Add a compatibility matrix for the supported ShenYu minor line(s).
• Add a reusable per-plugin E2E job contract: build the plugin and starter, launch a gateway with the external artifact, configure the plugin, exercise one success path and one failure/config-refresh path, and collect logs.
• Define how external middleware containers/services are provisioned and cached.
• Require unit tests for plugin code and starter auto-configuration.

Release and governance

• Document Maven coordinates, versioning, release cadence, and the cutover rule that prevents the same artifact from being published by both repositories.
• Add dependency, LICENSE/NOTICE, source/javadoc, signing, and reproducible-release checks required by ASF releases.
• Document the two-repository PR sequence and rollback procedure.
• Add a plugin inventory/compatibility table to the README.

Acceptance Criteria

• A clean checkout passes ./mvnw clean verify on JDK 17.
• CI executes build, unit tests, Checkstyle, RAT, and packaging for every PR.
• No migrated plugin silently skips unit tests.
• A reusable E2E workflow is documented and proven with at least one existing plugin.
• Plugin-store artifacts compile against the declared released ShenYu API/BOM.
• Publication ownership and version compatibility rules are documented.
• The contribution and PR templates reference commands that exist in this repository.

References

• Plugin store: https://github.com/apache/shenyu-plugin-store
• Existing Motan migration: [type:init] add motan plugin shenyu-plugin-store#1
• Existing TARS migrations: [type: refactor] init tarts plugin shenyu-plugin-store#2 and [type:init] add tars and motan starter shenyu-plugin-store#3