AOT source generator should output warnings instead of messages if partial keyword is missing

[lhak]

Proposal: The AOT source generator should output a warning instead of a message if the partial keyword is missing

Summary

To make an application AOT compatible, the partial keyword needs to be added to certain class definitions. The AOT source generator outputs a very useful message if they are missing. However, this message gets lost very easily as there are often a huge number of other messages (spell check, ...). As the app will in most cases not work correctly without this keyword, I think at least a warning should be output in the specific window and the build output window.

Rationale

• Currently, these messages are easily overlooked