Disallow (warn about) unused inames upon linearization

Warn if unused inames are present before linearizing kernel. This MR includes:

• New pre-schedule check for unused inames
• Unused inames in all test cases removed except for test_tim2d as discussed in this issue: precompute() calls in test_tim2d lead to unused inames
• New decorator remove_any_newly_unused_inames that may be applied to a transform to remove any unused inames resulting from that particular transform
• Applied this decorator function to realize_reduction and assignment_to_subst