Semantic logging

This is a PoC for using SemanticLogger in release-tools. This allows us to have much more fine-grained control over what gets displayed to the console, while also allowing us to log more things at various levels.

For example, we could log method parameters and API responses at a trace level, and not show them during spec runs on CI. This also allows us to remove the :silence_stdout and silence_stderr hacks, which break byebug and pry.

First step towards https://gitlab.com/gitlab-org/release-tools/issues/247