Ports somee infrastructure and converts Razor code generation tests to use
it. This makes it much easier to make cross cutting changes to code
generation and see the effect.
Use build /p:GenerateBaselines=true to update all of the generated code
in place or when adding new tests. Generally if tests are failing, the
easiest thing to do is to update the baselines and do a git diff to see
what the deltas are.
The changes to the tests here are to use the new baseline infrastructure
and to rename classes/methods to result in shorter file paths.
Adds a little more use of Razor extensibility.
Razor is a plugin model, so we can't be the 'first mover' for initiating
compilation in the build tools and IDE.
Reorganizes tests and fills out more reusable test infrastructure for
Razor-driven testing.
Adds tests for declaration-only configuration.