Add optional DDEV dev environment

Got further. We are now testing with a real memcached. I'm seeing some Heisen failures remaining. The tests sometimes fail locally and sometimes succeed, often changing when I enable or disable xdebug. Perhaps we are not clearing data sufficiently between test runs. Maybe someone else can take a look.

Also seeing similar failures trying to get them running them locally.

Looking at the first one in the CI output:

Drupal\Tests\memcache\Kernel\MemcacheBackendTest::testSetGet
Failed asserting that false is of type "object".
...
/builds/issue/memcache-3397864/web/core/tests/Drupal/KernelTests/Core/Cache/GenericCacheBackendUnitTestBase.php:143

It sets the data to cache then immediately gets it, getting false back from memcache instead of the cache object.

But that data IS there and IS being returned from memcache, just not from the memcache backend service.

Debugging locally it looks like data is being lost here where the backend checks the time against the bin last deletion time https://git.drupalcode.org/project/memcache/-/blob/8.x-2.5/src/MemcacheB...

Where timeIsGreaterThanBinDeletionTime is returning FALSE - and I can see during some tests the item microtime and the last bin deletion are the same.