Improve engine version-specific code handling

[tustanivsky]

Since Sentry plugin supports multiple Unreal Engine versions there is often a need to maintain its version-specific code. For instance, API that allows disabling Unreal's default crash-capturing mechanism appeared only in UE 5.2.

To handle version-specific code we're using #if-s combined with ENGINE_MAJOR_VERSION/ENGINE_MINOR_VERSION macro defined here. The existing checks like #if ENGINE_MAJOR_VERSION == 5 can be improved by making them more future-proof (i.e. for the situation when UE6 arrives) with something like ENGINE_MAJOR_VERSION != 4.

Another good example of how to check engine version can be found in EngineVersionComparison.h.