Handling of target properties in the C code generator is problematic

[lhstrh]

The C code generator creates a separate target config for each imported file and uses it specifically to handle the cmake-include and files target property, but ignores everything else. See CGenerator.inspectReactorEResource and GeneratorUtils.getLFResource.

Moreover, FederateGenerator implements a redundant but similarly ad-hoc handling of target properties from imported files (see #2080).

Instead, we should build a single TargetConfig and let the TargetProperty classes specify what the update behavior should be (e.g., override, append, etc.)