Non-square operator full assembly (#1316)

* Consistency formatting for operator tests

* Add (failing) test for non-square operator full assembly

* Add support for CPU-based full assembly of no

Non-square operator full assembly (#1316)

* Consistency formatting for operator tests

* Add (failing) test for non-square operator full assembly

* Add support for CPU-based full assembly of non-square CeedOperators

* Fix full assembly of identity quadrature functions and operators with CEED_BASIS_NONE

Also adds a unit test for full assembly which fails prior to the changes in this commit.

* Minor refactor to improve coverage

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