Rename all files related to the VANS solver using Fluid Dynamics prefix

[lpsaavedra]

Description

This PR changes the name of the main class and the name of the files related to the lethe-fluid-vans application. Is the second PR on a series of PRs that aim to rename all the Navier Stokes solvers of Lethe using the prefix FluidDynamics and removing GLS.

Testing

All the existent tests pass without any change.

Miscellaneous (will be removed when merged)

• The name of all the VANS assemblers had to be modified as well so that everything is uniform.

Checklist (will be removed when merged)

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Code related list:

• All in-code documentation related to this PR is up to date (Doxygen format)
• Lethe documentation is up to date
• The branch is rebased onto master
• Code is indented with indent-all and .prm files (examples and tests) with prm-indent
• Changelog (CHANGELOG.md) is up to date if the refactor affects the user experience or the codebase

Pull request related list:

• No other PR is open related to this refactoring
• Labels are applied
• There are at least 2 reviewers (or 1 if small feature) excluding the responsible for the merge
• If this PR closes an issue or is related to a project, it is linked in the "Projects" or "Development" section
• The PR description is cleaned and ready for merge