chore(nuget): update xunit.extensions to v1.9.0.1566

this enables testdriven.net to run tests and supports msbuild task to
run tests.
chore(test-sln): rename the test assembly name

Current name 'Jwc.Experimental' for test is conflicted with the product
project.
feat(assembly-level): restrict Experimental's references

The product project is allowed to add only specified references.