These are currently added implicitly by the compiler in the context of
`if`/`switch` expressions. In the future, there might be explicit
`then <expr>` statement useful for cases where one would like to add
more than one statement in the branch, to mark what value to actually
use.
See https://forums.swift.org/t/pitch-multi-statement-if-switch-do-expressions/68443
* `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`.
