With the introduction of semaphores in the blobmanager level, there's no
need for them in the benchmark tests now.

When running stress tests on blobs storage, we get weird errors when
hundreds of requests are made concurrently to the sqlite backend. This
commit adds a limit so only 10 requests will be delivered to the backend
at a time.

If there's no limit to the number of concurrent blob writes in the
server, the maximum limit of open files will eventually be reached, and
the processing of requests will start crashing. This commit adds
a semaphore to limit the number of concurrent writes in the server.

Related: #8973

With the set -o xtrace option all the variables are printed to stdout,
thus leaking all secrets in the CI output. This commit removes that
option from relevant scripts.

If pyzqm is built with --install-option, then all dependencies will be
forced to install from source. By removing that option, we allow pip to
use wheels.