Add Burgers 1D FD playground for temporal order-of-convergence study with IMEX-SDC (#639)

* Add Burgers 1D FD playground with MMS convergence study

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* Fix minor style issues from code review

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* Add burgers_1d_inhom_lift class with boundary lifting; update convergence script

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Co-authored-by: pancetta <7158893+pancetta@users.noreply.github.com>

Author: Copilot