Before this change, when somebody has requested the exact light class
we also store LazyJvmDiagnostic for it in a map inside DiagnosticHolder.
The problem is that LazyJvmDiagnostic retains a lot of memory:
GenerationState, bindingContext, etc.
At the same time, it commonly happens that light classes are being computed from Java resolve and diagnostics are obviously
unnecessary there.
The solution has two parts:
1. We don't retain diagnostics until somebody explicitly requested them
2. We force computation of LazyJvmDiagnostic to avoid retaining
backend's parts
The solution has a kind of drawback: for an opened in editor Kotlin file,
we'll run back-end twice for contained classes (analysis parts should be reused, though)
#KT-24048 Fixed
Denis Zharkov
b75024e3e0