Feature Request: Add a method in BindingGraphPlugin to know when all graphs are visited.

[arunkumar9t2]

Currently BindingGraphPlugin has only one method visitGraph which gets called for each BindingGraph.

However for component dependencies or any other use cases where we want access to Bindings in another graph currently it is not possible unless annotation processor output is manually post processed. A callback from Dagger when all graphs are processed would be helpful for the SPI plugin to collect all the graphs and perform work in this method where all bindings would be accessible.

This is similar to BindingGraphCapturer used in tests.

Use-case: Binding graph visualizations.