Refactor UnsteadyViscousBurgers as a subclass of UnsteadyInviscidBurgers solver

Issue/feature addressed

• Rename UnsteadyInviscidBurger class as UnsteadyInviscidBurgers (fix name typos)
• Consistently change test file names from InviscidBurger* to InviscidBurgers*
• Refactor UnsteadyViscousBurgers as a subclass of UnsteadyInviscidBurgers
• Remove unused forcing terms from UnsteadyInviscidBurgers

Proposed solution

Implementation

Tests

The following new tests have been added:

• solvers/ADRSolver/Tests/InviscidBurgers1D_WeakDG.xml
• solvers/ADRSolver/Tests/ViscousBurgers1D_WeakDG.xml
• solvers/ADRSolver/Tests/ViscousBurgers1D_WeakDG_IMEX.xml

Suggested reviewers

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Notes

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Checklist

• [ ] Functions and classes, or changes to them, are documented.
• [ ] User guide/documentation is updated.
• Changelog is updated.
• Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• [ ] License added to any new files.
• [ ] No extraneous files have been added (e.g. compiler output or test data files).