Continue having expression switch and raw string literals as preview language features for the start of JDK 13.
Per JEP 12 "Preview Language and VM Features" (JDK-8195734), preview language features are only available in the most recent release. JDK 12 has two preview language features switch expressions and raw string literals. Neither feature would be available in JDK 13 unless they are promoted to full language feature or continue in their preview status.
Continue the preview status of expression switch and raw string literals for the start of JDK 13.
This does not preclude additional change in status of those feature later in JDK 13, including removal from the release or graduation to a full language feature.
Continue preview status for expression switch and raw string literals.