SDK should not trigger generation of `.runtimeconfig` by compiler

Cesium Compiler has an inherent ability to generate `.runtimeconfig.json`. This ability is implemented mostly for the console compiler use.

Cesium SDK, on the other hand, relies on the `.runtimeconfig.json` generation introduced by the common .NET SDK (see #946 for details).

In the logs produced when compiling a project via Cesium SDK, there are also traces of the `.runtimeconfig.json` being generated by the compiler — which is then subsequently ignored.

To reduce the confusion, we should introduce an option for the compiler to skip generation of the `.runtimeconfig.json` — and this option should be utilized by the SDK, so that no redundant work is done or logged as being done.

The behavior of the current command-line compiler (generate the `.runtimeconfig.json` by default) should be left as-is.