Undo revert of connection kernels to pre-#192 (#220)

* Revert "Revert connection kernels to pre-#192 (#217)"

This reverts commit 35d4520e.

* Add custom iname tags to DirectDiscretizationConnection kernels

* Point req.txt for arraycontext, loopy

* Point req.txt loopy back to main

* Firedrake CI install: use loopy from git

* DirectCnx/InterpolationBatch: add, use _global_from_element_indices

* Do not update loopy in Fdrake CI for now

* Point req.txt back to main for arraycontext

* DirectConnection: add code path with in-place updates

* DirectConnection: revert kernel transforms back to old-style for non-inplace kernels

* Ensure test coverage of non-inplace DirectConnection kernels

* InterpolationBatch: Drop transform strategy based on iname tags for now

* DirectDiscretizationConnection: Fix kernel names, hash keys