Add logging levels / hide pip messages

[MetricMike]

Is your feature request related to a problem? Please describe.

asdf install awscli X is loud and includes messages like:

~/.asdf/installs/awscli/2.1.25 ~/projects/dev-environment
Collecting pip
  Using cached pip-21.0.1-py3-none-any.whl (1.5 MB)
Collecting setuptools
  Using cached setuptools-53.0.0-py3-none-any.whl (784 kB)
Collecting wheel
  Using cached wheel-0.36.2-py2.py3-none-any.whl (35 kB)
Installing collected packages: pip, setuptools, wheel
  Attempting uninstall: pip
    Found existing installation: pip 20.2.3

Those should be hidden.

Describe the solution you'd like

Unless ASDF_AWSCLI_LOG=DEBUG is present, don't print those messages.