Selective Loading to speed up execution

[CharliePoole]

This issue came up on SO: https://stackoverflow.com/questions/49195224/testcasesource-attribute-reads-all-the-test-datas-of-existing-tests-even-if-we

If you run the console with a filter, the ideal result would be to only load those test that will be selected by the filter, avoiding running any TestCaseSource code for those that will not be selected. However, this is not possible in general because some filters may only be applied after the test has been loaded. We would have to analyze the filters to determine which ones may be applied before loading, using the elements available through reflection. For example, a class filter would be easy enough to do while a test filter that included the names of method arguments would not be.

For this issue, I suggest we do the low-hanging fruit first. We could use the test argument but limit it to values that specify namespace or class, not method name. The framework already supports the LOAD package setting, which will cause only those items in a list of names to be loaded in the first place.