Improved HDL simulation flow for Questa (#47)

* Updated to use vlog, vcom, vopt and vsim directly with dependency management instead of scripts.
* Updated to support testcases.
* Updated to make the testcase generator and test cases work.
* Updated to compile all parameter sets enabling run-time selection and updated to merge coverage
* Add VsimFlags option.
* Fixed whitespace. Updated to be able to simulate all parameter sets.
* Fixing formatting using 'go fmt' and converted tabs to spaces.
* Made functions not needed elsewhere private.
* Updated how coverage data is generated; added flag to generate HTML coverage database.
* Added Vivado xsim support.
* Updated formatting.
* Added descriptions to variables.
* Removed check for valid parameter set as it doesn't work when all targets are evaluated.
* Changed name of optimized design to avoid name collisions.
* Updated to run final blocks too.
* Updated to also add a dependency on the testcase generator if available.
* Fixed problem where a compilation error did not make the build process fail. Also made naming of directories a bit more sane.
* Updated based on review feedback to accept comma-separated testcases and params. Improved dbt build output to reflect command usage. Outputs coverage database location when enabled.

Co-authored-by: Niels <Niels Haandbaek>

RULES/hdl/hdl.go

@@ -25,6 +25,7 @@ type Ip interface {
 }
 
 type Library struct {
+	Lib       string
 	Srcs      []core.Path
 	DataFiles []core.Path
 	IpDeps    []Ip