Lets us sever the dependency between stats & exec ctx (finally).
More work likely needs to go into the *mechanism* used here (I'm not a
fan of the per thread index), but that's also something we can address
later.
* [WIP] EventEngine::Run microbenchmarks
* Add fanout impl and fix tracking of time spent doing work in threads
* tune down benchmarks; fix fanout counting logic.
* tune down closure fanout tests
* format
* odr
* reviewer feedback
* unify some fanout logic; add a large-AnyInvocable test
lambdas that take an allocation are about 10x slower
* reviewer feedback
* fix invalid vector access
* rm DNS
* format
* copy params for each lambda callback
This fixes segfaults when we cannot ensure all callbacks are complete
before exiting the test.
* s/promise/Notification/g bm_exec_ctx
* ODR and leak
* fix division by zero
* fix