Merge graphintrospection lib back into graphqlservice

[wravery]

Originally, I split code which was only referenced by schemas generated without schemagen --no-introspection into a separate library called graphqlintrospection. At some point, I ended up adding references to every cpp/object file in graphqlintrospection to graphqlservice and the schemas generated by schemagen (mostly for request validation support). Even though a schema build with schemagen --no-introspection doesn't expose the __schema or __type field resolvers, it still needs to know about built-in types and use them for validation. The dependency was hidden in all of the nointrospection tests by the part of CMakeLists.txt which added a dependency from graphqljson on graphqlintrospection.

It's simplest overall to just merge graphqlintrospection back into graphqlservice. The build requirements are less complicated both internally and for consumers. This should be source-compatible with schemas/services built with v4.0.*, but since it will probably require a change to the build system for consumers, I'm also bumping the minor version to v4.1.0.