Chore cleanup turbo functions

[EvertBunschoten]

Proposed Changes

Clean up the turbomachinery functions in CEulerSolver.cpp and apply SU2 coding rules.

Related Work

PR Checklist

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• I have added a test case that demonstrates my contribution, if necessary.
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[pcarruscag]

@joshkellyjak do you want to take a look too?

[joshkellyjak]

Will have a look this week, thanks Evert!