Do not print project configuration on every invocation

While showing the effective configuration bst is running in can be a useful debugging tool, it really clutters the tool's output and most of the times scrolls by too fast to evaluate anyway. When using bst on a terminal it really adds to the clutter of printed output and making it really hard to scroll to navigate anywhere in that shell.

IMHO it should be shown only when a flag like `--print-configuration` or just `--verbose` is given and not otherwise.

I can understand why it is useful for CI environments to always show it, but for those cases I feel like it should just be controlled by the verbose flag and CI environments should configure that.

Start at the BuildStream CLI entry point and trace where the effective project configuration is printed during a normal invocation. Compare the proposed --print-configuration and --verbose behaviors, then verify that ordinary terminal output is quieter while an explicit flag still shows the configuration, including the CI use case.

Written by the indexing model from the issue text.