set executable bit on Linux/MacOS as that's what determines whether something
is executable. Also simplify partial path creation, only remove up to the first
colon, so those filesystems which have a single root are treated properly
This restructuring moves tests to a directory name which matches the module
in which the cmdlet resides which should improve the discoverability of a
specific test.
For tests which are not about cmdlets in a module, new directories have been
created to make those tests easier to find as well
James Truher