feat: concurrent storage put (#1304)

* feat: concurrent storage put

* add a build tag for stress testing

* enable storage put stress test

* write labels in a single transaction

* make cache.GetOrCreate atomic

* adjust test params

* fix cache GetOrSet persistence flag

* add storage queue params

* set default workers to 1

Co-authored-by: Dmitry Filimonov <dmitry@pyroscope.io>