Support terraform multi-hop connections

[gruebel]

Describe the issue
Create cross-variables edges between resources when building terraform graph (based on the variable rendering).

in the _build_edges step - try to mark the resources that have an out edge to variable/local/etc in order to search for cross-variable edges only for these resources.

add a _build_cross_variable_edges step after the variable rendering (add to the graph only edges that didn’t exist before).

mark the cross-variable edges label with a prefix of [cross-variable]

Add env variable in checkov (CHECKOV_EXPERIMENTAL_CROSS_VARIABLE_EDGES) for enabling the new logic

[gruebel]

Added via #3920