(dev/core#1412) E2E - Add test case for path+URL construction in CLI

(dev/core#1412) E2E - Add test case for path+URL construction in CLI

Overview
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In dev/core#1412, the regression involved CLI processes producing incorrect URLs.
This adds some test-coverage.

Before
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No test coverage for URLs in CLI environment.

After
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There is some test-coverage. It's able to reveal the existence of the bug from 1412.

Comments
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A lot of path/URL construction is dependent on the environment/site-build.
The test does not, on its own, guarantee that all environments work.
Rather, it adds a new slice of cheese to the stack.

This slice is moderately generic - in that I've successfully tested it
localy on `drupal-demo` and `wp-demo` builds.  In theory, it should work on
other build types (as long as they set variables `CIVI_CORE`, `CMS_ROOT`,
`CMS_URL`).