Changed read_tcp to use report_runtime when routing differential & hierarchical nets

[DallonTG]

Previously, tincr::read_tcp wasn't using the report_runtime procedure to measure the time it takes for Vivado to route differential nets and hierarchical port nets. It was previously thought that we needed to manually measure the time when using the route_design command, but the syntax was just tricky.

This PR just improves the code a little bit by using report_runtime correctly now.