Physics: Enable liquid mesh generation by default

Previously mesh generation was disabled by default. This meant it was
only visible for wireframe or x-ray in the viewport, and not visible
in renders.

Pull Request: https://projects.blender.org/blender/blender/pulls/120832

source/blender/makesdna/DNA_fluid_defaults.h

@@ -66,7 +66,7 @@
     .maxres = 32, \
     .solver_res = 3, \
     .border_collisions = 0, \
-    .flags = FLUID_DOMAIN_USE_DISSOLVE_LOG | FLUID_DOMAIN_USE_ADAPTIVE_TIME, \
+    .flags = FLUID_DOMAIN_USE_DISSOLVE_LOG | FLUID_DOMAIN_USE_ADAPTIVE_TIME | FLUID_DOMAIN_USE_MESH, \
     .gravity = {0.0f, 0.0f, -9.81f}, \
     .active_fields = 0, \
     .type = FLUID_DOMAIN_TYPE_GAS, \