DRILL-5104: Foreman should not set external sort memory for a physical plan
Physical plans include a plan for memory allocations. However, the code
path in Foreman replans external sort memory, even for a physical plan.
This makes it impossible to use a physical plan to test memory
configuration.
This change avoids changing memory settings in a physical plan; while
preserving the adjustments for logical plans or SQL queries.
Revised to put a property in the plan itself. Old plans, and those
generated from SQL, will have memory allocations applied. Plans
marked as already "resource management" planned will be used as-is.
Includes a unit test that demonstrates the new behavior.
close apache/drill#703
