Consistently use relative tolerance for GMRES

Issue/feature addressed

Currently, the Newton solver converts the relative tolerance into an absolute tolerance and m_rhs_magnitude is set to 1.0 in the GMRES solver. While the current implementation behaves properly for the compressible flow solver, the use of GMRES solver will result in the use of an absolute tolerance with the incompressible Navier-Stokes solver. This is probably not the intended behavior. This MR solves this issue.

Proposed solution

Implementation

Tests

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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).