FLUID-5088: Improved diagnostics for circular or failed expansion process

 - option path is now propagated up to the site where expansion fails, allowing more intelligible error messages. This enables merging and expansion to be put back into correspondence in terms of signatures and circularity detection strategy, and allows the removal of the old "weak" circularity detection "guardCircularity" that could only operate on units of entire Fluid components. Adding this feature removes a net 4 lines of code from FluidIoC!