- Previously, `KtFirAnonymousObjectSymbol` was a
`KtEnumEntryInitializerSymbol`, which carried the risk that an
anonymous object unrelated to enum entries might be used as an enum
entry initializer. This commit introduces a specific symbol for FIR
enum entry initializers.
- As a nice side effect, anonymous object symbol creation is simplified
and `KtFirEnumEntryInitializerSymbolPointer` can restore the symbol
via `KtFirEnumEntrySymbol.enumEntryInitializer`.
^KT-61425