* visiting now happens in a later stage than fetching labels. While
fetching a list of entities to be visited is created, and then acted
upon in actual extraction. This partially flattens the recursive
nature of `fetchLabel` into a loop inside `SwiftVisitor::extract`.
Recursion in `fetchLabel` will only happen on labels fetched while
naming an entity (calling into `SwiftMangler`).
* The choice whether to name a declaration or type has been moved from
the translators to `SwiftMangler`. Acting on this choice is contained
in `SwiftDispatcher::createLabel`.
* The choice whether to emit a body of a declaration has been moved from
`DeclTranslator` to the dispatcher. This choice is also contained in
`SwiftDispatcher::createLabel`.
* The simple functionality of the `LabelStore` has been moved to the
`SwiftDispatcher` as well.
This is done by adding a `isSuccessfullyExtracted` predicate that is
filled for primary files at the very end of the extractor invocation if
the frontend was performed successfully. If for example the extractor
crashes this will therefore not be filled.
The upgrade script is written so that `SuccessfullyExtractedFiles.ql`
on an upgraded script will give exactly the same results as before it.
While the internal registry was being cleaned up from files removed by
codegen itself, it was not dropping files removed outside of codegen.
Because of this files removed by the user were not being regenerated
again if no change was staged to them, unless `--force` was provided.
This also fixes some such "ghost" entries in the registry and some
missing generated files.
This refactors SelfApplyExpr.getFunction() as MethodLookupExpr().getMethodRef().
This is simpler, because we are not hiding DeclRefExprs or reinventing hidden AST resolution.
