Standardize Test Execution

[gallardo]

This PR standardizes unit test execution while preserving backward compatibility and enabling native IDE integration.

Changes:

• Enhanced testSingle:
  • Enabled Standard Test Selection: Fully supports test case selection via --tests (default convention in Gradle).
  • Keeps Default Behavior: Defaults to TestCmsSystemInfo* when no explicit property or filter is provided.
  • Legacy Property Support: Fully supports -PtestCaseToRun=<TestClass> property, emitting a deprecation warning but functioning exactly as before.
• Simplified test task: Always executes org.opencms.test.AllTests for backward-compatible CI behavior.
• Enhanced test configuration:
  • Refactored code of test tasks to eliminate redundancy.
  • Fixed testImplementation to extend setupImplementation for correct classpath.

Usage:

# Run the complete test suite (CI default)
./gradlew test

# Run the default testSingle behavior (TestCmsSystemInfo*)
./gradlew testSingle

# Run a specific test using testSingle with --tests
./gradlew testSingle --tests org.opencms.i18n.TestCmsEncoder.testDecodeHtmlEntities

Verification:

The following validations were performed to ensure parity, backward compatibility, and IDE integration:

• Backward Compatibility:
  • Verified that ./gradlew testSingle (without arguments) executes TestCmsSystemInfo* as before.
  • Confirmed that ./gradlew test executes org.opencms.test.AllTests, maintaining consistent CI behavior.
• IDE Integration: Verified that IDEs can execute individual tests using the test task with native --tests filtering without conflicts (See notice below).
• Explicit Filters: Confirmed that ./gradlew testSingle --tests <ClassName> and ./gradlew testSingle --tests <ClassName.methodName> correctly override the default and run only the specified tests (See notice below).

Notice on Gradle Test Filtering and JUnit 3 Suites

When using legacy JUnit 3 tests that implement a public static Test suite() method, Gradle's --tests Class.method filtering does not apply at the method level as one might expect. In this case, JUnit executes exactly the tests returned by the suite (typically the whole test class), which overrides Gradle's method-level selection. This is expected behavior of JUnit 3's suite-based execution model, not a Gradle bug. Tests without a suite() method use default discovery and therefore support method-level filtering correctly.

[gallardo]

I want to test this PR a bit more before giving it the green light for review.

[gallardo]

I have split this PR into two commits to allow selectively removing the old selection logic based on the non-standard testCaseToRun property.