Re #6193. Remove longer test put in when we had some failures.

...since resolved.
Re #6193. Reduce the sizes of the workspaces tested.

Also re-use workspaces where possible rather than creating identical
ones over and over again. Note that this is not always possible as
in some instances the input workspace is modified.
Re #6193. Reduce the sizes of the workspaces tested.

Also re-use workspaces where possible rather than creating identical
ones over and over again. Note that this is not always possible as
in some instances the input workspace is modified.
Re #6193. Slim down 'grouped' tests.

Fewer pixels & events, otherwise unchanged.
Re #6193. Slim down BinaryOperationTest.

There's no way that last test needed to be that big.
Merge remote-tracking branch 'origin/feature/6193_slim_down_binary_op_tests'