enable dpi_dasm for coverage model across all simulators

Created by: strichmo

PR enables the new ISA cov model (and the DPI_DASM built on Spike) in all simulators by default. define for DPI_DASM is removed Checked in Linux64 verison of dpi_dasm shared library that should work across simulators (tested with xrun, vsim and dsim) Made attempts to update VCS and Riviera but not tested make dpi_dasm should work by default on Xcelium and Mentor (target only needed to edit, rebuild dpi_dasm shared lib)

Note that the coverage model is still disabled (run-time) by default until covergroups are implemented and tested.