[Merged by Bors] - add tracing spans for parallel executor and system overhead#3416

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hymm wants to merge 2 commits intobevyengine:mainfrom hymm:more-tracing-spans

+15-2

Commits on Dec 22, 2021

add tracing spans for executor and system overhead
hymm
committed

Commits on Dec 23, 2021

run cargo fmt
hymm
committed