feat: set DD_PROFILING_MEMORY_ENABLED to true

[rayzhou-bit]

Datadog recommends this setting be turned on with APM profiling. This PR follows turning on APM profiling in stage, edge and prod.

edx/edx-arch-experiments#749

Make sure that the following steps are done before merging:

• Have a Site Reliability Engineer review the PR if you don't own all of the services impacted.
• If you are adding any new default values that need to be overridden when this change goes live, update internal repos and add an entry to the top of the CHANGELOG.
• Performed the appropriate testing.