* `variables` under `CaseStmt` are now AST children, which solves
orphan `VarDecl`s in that case
* reordered `CaseStmt` AST children to be `labels > variables > body`
(was `body > labels`)
* made `NamedPattern::getVarDecl` an extracted property instead of
`getName`
* The above led to duplicate DB entities because of a quirk in the
Swift compiler code. This is solved by tweaking the extraction of
`variables` under `CaseStmt` to not use `getCaseBodyVariables`.
Add module context to all declarations. As keeping the `std::variant`s
required slightly more work for this, and we intended to remove them
any way, this is done in this change.
For background, we put those in as we were not extracting all modules at
the time, so we were missing some DB ids that we put back in by adding
the "defining" traps not only in the trap file related to the defining
module but also to the one where the declaration was used. Since then
we fixed module extraction, so this should not be needed any more.
Deduplication of `ConcreteVarDecl` is triggered only if its
`DeclContext` is not local. This avoids a mangled name conflict.
Also added more thourough tests for `ConcreteVarDecl` and `ParamDecl`.
