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>

sources/test/jest/cache-service-loader.test.ts

@@ -0,0 +1,50 @@
+import {describe, expect, it, jest, beforeEach} from '@jest/globals'
+
+import {CacheProvider} from '../../src/configuration'
+import type {CacheConfig} from '../../src/configuration'
+
+describe('getCacheService selection logic', () => {
+    beforeEach(() => {
+        jest.restoreAllMocks()
+    })
+
+    it('returns NoOpCacheService when cache is disabled', async () => {
+        const {getCacheService} = await import('../../src/cache-service-loader')
+        const mockConfig = {
+            isCacheDisabled: () => true,
+            getCacheProvider: () => CacheProvider.Enhanced,
+            isCacheLicenseAccepted: () => true
+        } as unknown as CacheConfig
+
+        const service = await getCacheService(mockConfig)
+        const report = await service.save('/home/.gradle', [], {
+            disabled: true,
+            readOnly: false,
+            writeOnly: false,
+            overwriteExisting: false,
+            strictMatch: false,
+            cleanup: 'never',
+            includes: [],
+            excludes: []
+        })
+
+        // NoOpCacheService returns a specific report mentioning cache was disabled
+        expect(report).toContain('Cache was disabled')
+    })
+
+    it('wraps BasicCacheService with LicenseWarningCacheService when cache-provider is basic', async () => {
+        const {getCacheService} = await import('../../src/cache-service-loader')
+        const mockConfig = {
+            isCacheDisabled: () => false,
+            getCacheProvider: () => CacheProvider.Basic,
+            isCacheLicenseAccepted: () => false
+        } as unknown as CacheConfig
+
+        const service = await getCacheService(mockConfig)
+
+        // The service should not be a bare BasicCacheService — it should be wrapped
+        // with LicenseWarningCacheService that appends the basic caching summary
+        const {BasicCacheService} = await import('../../src/cache-service-basic')
+        expect(service).not.toBeInstanceOf(BasicCacheService)
+    })
+})