[Dam/FreeSurf] Change in Dam joints and improvements in both apps examples

[joaquinirazabal]

In this PR the joints in the DamApp were changed to use the joints in the PoromechanicsApplication from Kratos.

Regarding the examples:

• 2D and 3D examples of the DamApp were corrected
• The 2D example of the FreeSurfaceApp was improved
• A new 3D example of the FreeSurfaceApp was created

I also add again the FreeSurfaceApp to the initial menu inside the Fluids part.

[joaquinirazabal]

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