IDEA-113632 - Fix Geb Page content not being available

[Poundex]

Fixes IDEA-113632

When using Page objects, Geb makes the content from the Page definition available. However, IJ is currently not recognising this:

This change makes content from the current detected Page available:

Any method which changes the Page (to(), via(), page()) or asserts the current page (at()) will modify the current page, and only content from the last detected page will be in scope. The dynamic variables have the correct type, and navigate correctly back to their definitions in the Page. Completion is also working as expected: