Update agent pprof rpcs to streaming

[drewbailey]

Issue

Improve upon #6841 to use streaming rpc endpoints so that the entire profile isn't loaded into memory. On a buys client or server a long run trace profile can reach near 100mb. Streaming would alleviate some of the memory burden on the server instead of loading it entirely in memory.

See #6841 (comment) for memory characteristics of various profiles.