MAINT: linalg.qr: add modes 'reduced', 'complete', 'raw'.

This updates the new modes. The 'reduced' mode replaces 'full' and 'thin',
the 'complete' mode replaces 'big', and the 'raw' mode is new. Both the
older modes 'full' and 'economic' are deprecated.
MAINT: linalg/tests: Test the new modes.

Use the  new modes 'reduced' and 'complete' in the tests instead of
'full' and 'big'. Test 'raw' instead of 'economic', and test for the
deprecation of the old modes 'full' and 'economic'.