FIRST COMMIT: Swift Test: Add HTML coverage report

When executing tests, we often want to see a coverage report.  This add
an HTML option.

Author: bkhouri

.swiftpm/configuration/coverage.html.report.args.txt

@@ -0,0 +1,15 @@
+--project-title="output is tmp foo.bar"
+--tab-size=10
+--coverage-watermark=80,20
+--enable-vtable-value-profiling
+--show-branch-summary
+--show-region-summary
+--show-branches=percent
+--show-mcdc-summary
+--show-expansions
+--show-instantiations
+--show-regions
+--show-directory-coverage
+--show-line-counts
+
+--output-dir=/tmp/foo.bar