Add open-source 'basic' cache provider and revamp licensing documentation (#930)

## Summary

- **New `basic` cache provider**: Adds an open-source (MIT-licensed)
caching implementation built on `@actions/cache` as an alternative to
the proprietary Enhanced Caching. Users can opt in with `cache-provider:
basic` on both `setup-gradle` and `dependency-submission` actions.
- **Revamped licensing & distribution docs**: Replaces the verbose
licensing notice block (previously shown in README, docs, and logs) with
a friendlier callout and a new dedicated
[DISTRIBUTION.md](./DISTRIBUTION.md) covering component licensing, usage
tiers, data privacy ("Safe Harbor"), and opt-out instructions.
- **Improved messaging**: Enhanced Caching and Basic Caching each
display concise, informative log messages and job summary notes instead
of the previous wall-of-text license warning.
- **New integration tests**: Adds `integ-test-basic-cache-provider.yml`
workflow that seeds and verifies the basic cache provider across
platforms, plus unit tests for `BasicCacheService` and `getCacheService`
selection logic.
- **CI workflow reorganization**: Dependency-submission integration
tests extracted into their own reusable suite
(`suite-integ-test-dependency-submission.yml`); sample project tests
moved into the caching suite.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -2,21 +2,14 @@
 
 This repository contains a set of GitHub Actions that are useful for building Gradle projects on GitHub.
 
-> [!IMPORTANT]
-> ## Licensing notice
+> [!NOTE]
+> ### ⚡️ Choice of caching providers in v6
+> To provide the fastest possible build experience this action includes **Enhanced Caching** via `gradle-actions-caching`, an optimized provider powered by proprietary technology. This feature is **free for all public repositories** and is currently available as a **Free Preview** for private repositories. 
 >
-> The software in this repository is licensed under the [MIT License](LICENSE).
+> **Prefer a 100% Open Source (MIT) path?**
+> We also provide a **Basic Caching** provider as a thin wrapper over `actions/cache`. This provider is **free for all repositories** (public and private) and can be enabled at any time by setting `cache-provider: basic`.
 >
-> The caching functionality in this project has been extracted into `gradle-actions-caching`, a proprietary commercial component that is not covered by the MIT License for this repository. 
-> The bundled `gradle-actions-caching` component is licensed and governed by a separate license, available at https://gradle.com/legal/terms-of-use/.
->
-> The `gradle-actions-caching` component is used only when caching is enabled and is not loaded or used when caching is disabled.
->
-> Use of the `gradle-actions-caching` component is subject to a separate license, available at https://gradle.com/legal/terms-of-use/. 
-> If you do not agree to these license terms, do not use the `gradle-actions-caching` component.
-
-This license notice will be displayed in workflow logs and each job summary. To suppress this message, 
-either [accept the terms of use](docs/setup-gradle.md#publishing-to-scansgradlecom) in your workflow, or [provide a Develocity access key](docs/setup-gradle.md#managing-develocity-access-keys).
+> For a full breakdown of the components, usage tiers, and our **Safe Harbor** data privacy commitment, see our [Distribution & Licensing Guide](./DISTRIBUTION.md).
 
 ## The `setup-gradle` action