Do not specify "name" when using pip install --editable

This fixes #6025 by setting "name" to an empty string if the "editable"
param is used, like is already being done for the "requirements" param.
Merge pull request #6037 from terminalmage/issue6025

Do not specify "name" when using pip install --editable
Pass __env__ to salt.modules.pip._get_cached_requirements

This fixes #6003, and resolves a traceback caused by the environment not
being passed to the function.
Merge pull request #6043 from terminalmage/issue6003

Pass __env__ to salt.modules.pip._get_cached_requirements