mxcli test: override constants per run or per test #1700

What happens: a test cannot set a constant, so a switch driven by a constant (for example a mock that fails on demand) cannot be tested end to end.
Expected: @constant Module.Name = value in a test block, or --constant Module.Name=value on mxcli test.
Version: 0.28.0.

Mendix 11.12.4.