ObjStorage: investigate the per-request CPU overhead of aiohttp

https://magic.io/blog/uvloop-blazing-fast-python-networking/

"However, the performance bottleneck in aiohttp turned out to be its HTTP parser, which is so slow, that it matters very little how fast the underlying I/O library is."

-> This means we should probably change the HTTP library if we want to do one HTTP request per object we retrieve.

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Migrated from T1596 (view on Phabricator)