Some editors use diagnostics from SourceKit to replace build issues. This causes issues if the diagnostics from SourceKit are formatted differently than the build issues. Make sure they are rendered the same way, removing most uses of `DiagnosticsEditorMode`.
To do so, always emit the `add stubs for conformance` note (which previously was only emitted in editor mode) and remove all `; add <something>` suffixes from notes that state which requirements are missing.
rdar://129283608
The cached values for `hasOnlyCasesWithoutAssociatedValues()` and
`hasPotentiallyUnavailableCaseValue()` are computed in a single pass over the
elements of an `EnumDecl`. However, the pass would return early after finding
an element with an associated value, without checking whether any of the rest
of the elements were potentially unavailable. This made `Comparable` synthesis
succeed for any enum with potentially unavailable elements so long as the first
element in the enum has an associated value.
