promote stackprof into a production gem

From dicussion #30181 (comment 279586362).

At the moment, stackprof is in :development, :test group in Gemfile. In production (such as Omnibus docker container), stackprof gem is not available by default.

As experienced in issue #30181 (comment 279273638), it is not very straight-forward to install stackprof in Omnibus docker container. There are unmet dependencies(ruby.h header file, incompaible openssl.so).

As a sampling profile tool, stackprof is helpful in production-alike environment #30181 (comment 279180229).

So we want to promote stackprof into a production gem. To achieve this, I think we need to:

• Update Gemfile (In gitlab project)
• Update Omnibus package to meet stackprof dependencies (in Omnibus project)