PHPLIB-1698 Remove tests for Atlas Data Lake

[GromNaN]

Fix PHPLIB-1698.

ADL will be shut down on September 30, 2025.

This PR targets the branch 1.21 so that the ADL jobs are not failing once support is removed in evergreen. Spec tests are updated in #1777

[Copilot]

Pull Request Overview

This PR removes Atlas Data Lake testing support from the MongoDB PHP library in preparation for Atlas Data Lake's shutdown on September 30, 2025. The changes ensure that ADL-related tests and CI jobs don't fail once support is officially removed.

Key changes:

• Removes all Atlas Data Lake test classes and methods
• Eliminates ADL-specific CI configuration and test execution scripts
• Cleans up utility methods for ADL detection

Reviewed Changes

Copilot reviewed 9 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/UnifiedSpecTests/UnifiedSpecTest.php	Removes ADL test methods and data providers
tests/SpecTests/AtlasDataLakeSpecTest.php	Deletes entire ADL spec test class file
tests/FunctionalTestCase.php	Removes isAtlasDataLake() utility method
.evergreen/run-tests.sh	Removes ADL test case from test runner script
.evergreen/config/test-variants.yml	Removes ADL test variant configuration
.evergreen/config/test-tasks.yml	Removes ADL test task definition
.evergreen/config/templates/test-variant/phpc.yml	Removes ADL test from task list
.evergreen/config/templates/test-variant/modern-php-full.yml	Removes ADL test from task list
.evergreen/config/functions.yml	Removes ADL test execution function

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