Pull the tb.v top module name from info.yaml

[gojimmypi]

One less place to manually edit project name:

Updates testbench Makefile to pull module name into a macro called TT_TOP_MODULE from project info.yaml file.

When otherwise not defined, the old tt_um_example name is assumed.

This is also helpful when synchronizing code between foundries such as SKY130 and GF180 unique top module names.

I've done this in my dev branch and also added to my ULX3S test (see also #22 and related pull requests for ULX3S support)