Don't JIT warmup docs, nor count them as Eval.JitProfileInterpRequests.

Summary: Don't JIT warmup docs, nor count them as Eval.JitProfileInterpRequests,
because they are not normal requests.

Rename Eval.JitWarmupRequests to Eval.JitProfileInterpRequests, in order
to distinguish interpreted profiled requests from warmup requests that
have no purpose besides loading metadata into memory.

Reviewed By: @jasone

Differential Revision: D1502407