Fix condition in prefixIsElidable to prevent compiler crash

[szymon-rd]

Fix #18901

The check in prefixIsElidable was defined as follows:

tp.symbol.isParamOrAccessor && !pre.cls.is(Trait) && ctx.owner.enclosingClass == pre.cls

I assume that !pre.cls.is(Trait) condition was introduced to accommodate for Mixin phase getting rid of ParamAccessor defined in traits. However, the prefix does not indicate where the symbol is really defined - it only represents the prefix from the perspective of the current template, so it could be inherited. When it's inherited from a trait, the prefix would be the current class, but the member still is defined in the trait, and Mixin would get rid of the ParamAccessor flag. Therefore, I changed this condition to the following:

tp.symbol.isParamOrAccesso && !pre.cls.is(Trait) && !tp.symbol.owner.is(Trait) && ctx.owner.enclosingClass == pre.cls

[szymon-rd]

It fails a lot of CC tests (for some reason only CC and captures)

[szymon-rd]

Now it's passing