Add the yappi profiler for multithread profiling

[boxysean]

helps #6073 but does not resolve

Description

I am opening this PR for instructional purposes. Please advise if this is worthy change, or perhaps we just document how to profile with yappi.

Adds yappi for multi-threaded profiling. Warning: considerably slows down runtime, in my case 15 minute call turned into 3 hours.

(Alternative considered but not tried: could we avoid this change and just call dbt with yappi from the CLI ?)

Since dbt spawns 100+ threads (?!) this creates 100+ pstat files:

➜  pstat_models_7_with_change $ ls
thread-0.pstat        thread-116.pstat      thread-15.pstat       thread-33.pstat       thread-51.pstat       thread-7.pstat        thread-88.pstat
thread-1.pstat        thread-117.pstat      thread-16.pstat       thread-34.pstat       thread-52.pstat       thread-70.pstat       thread-89.pstat
thread-10.pstat       thread-118.pstat      thread-17.pstat       thread-35.pstat       thread-53.pstat       thread-71.pstat       thread-9.pstat
thread-100.pstat      thread-119.pstat      thread-18.pstat       thread-36.pstat       thread-54.pstat       thread-72.pstat       thread-90.pstat
thread-101.pstat      thread-12.pstat       thread-19.pstat       thread-37.pstat       thread-55.pstat       thread-73.pstat       thread-91.pstat
thread-102.pstat      thread-120.pstat      thread-2.pstat        thread-38.pstat       thread-56.pstat       thread-74.pstat       thread-92.pstat
thread-103.pstat      thread-121.pstat      thread-20.pstat       thread-39.pstat       thread-57.pstat       thread-75.pstat       thread-93.pstat
thread-104.pstat      thread-122.pstat      thread-21.pstat       thread-4.pstat        thread-58.pstat       thread-76.pstat       thread-94.pstat
thread-105.pstat      thread-123.pstat      thread-22.pstat       thread-40.pstat       thread-59.pstat       thread-77.pstat       thread-95.pstat
thread-106.pstat      thread-124.pstat      thread-23.pstat       thread-41.pstat       thread-6.pstat        thread-78.pstat       thread-96.pstat
thread-107.pstat      thread-125.pstat      thread-24.pstat       thread-42.pstat       thread-60.pstat       thread-79.pstat       thread-97.pstat
thread-108.pstat      thread-126.pstat      thread-25.pstat       thread-43.pstat       thread-61.pstat       thread-8.pstat        thread-98.pstat
thread-109.pstat      thread-127.pstat      thread-26.pstat       thread-44.pstat       thread-62.pstat       thread-80.pstat       thread-99.pstat
thread-11.pstat       thread-128.pstat      thread-27.pstat       thread-45.pstat       thread-63.pstat       thread-81.pstat       thread-combined.pstat
thread-110.pstat      thread-129.pstat      thread-28.pstat       thread-46.pstat       thread-64.pstat       thread-82.pstat
thread-111.pstat      thread-13.pstat       thread-29.pstat       thread-47.pstat       thread-65.pstat       thread-83.pstat
thread-112.pstat      thread-130.pstat      thread-3.pstat        thread-48.pstat       thread-66.pstat       thread-84.pstat
thread-113.pstat      thread-131.pstat      thread-30.pstat       thread-49.pstat       thread-67.pstat       thread-85.pstat
thread-114.pstat      thread-132.pstat      thread-31.pstat       thread-5.pstat        thread-68.pstat       thread-86.pstat
thread-115.pstat      thread-14.pstat       thread-32.pstat       thread-50.pstat       thread-69.pstat       thread-87.pstat

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry