feature: gazelle wrapper allows to pass environment variables (#1438)

* feature: gazelle wrapper allows to pass environment variables

In certain cases it may be useful to have predefined values like
GONOSUMDB or others passed into the gazelle helper, with this change
the caller to helper can pass those values, and make them part of
the code tree instead of a mess of environment variables in the
command line

* feature: wrapper validates environmental variables

Now we properly validate environmental variable names and also properly
quote values to avoid environment escaping injection.

Adding some unit tests to make sure things work as expected