Assign Return Value To New Variable for switch expressions

### Description

The hint Assign Return Value To New Variable is available for most expressions, but not for switch expressions.

### Use case/motivation

Example:
```java
enum FooBar { FOO, BAR };
FooBar fooBar = FooBar.FOO;
switch (fooBar) { case FOO -> 10; case BAR -> 20; };
```
The hint should be available on the *switch* line and result in:
```java
int [name] = switch (fooBar) { case FOO -> 10; case BAR -> 20; };
```
For comparison, it is available on:
```java
fooBar == FooBar.FOO ? 10 : fooBar == FooBar.BAR ? 20 : -1;
```
The usefulness should hopefully be obvious.

### Related issues

_No response_

### Are you willing to submit a pull request?

No

Start by locating the implementation of the “Assign Return Value To New Variable” hint and the existing handling for other expressions. Trace how the hint determines the expression type, then verify that applying it to a switch expression produces the declaration shown in the issue and preserves the switch result.

Written by the indexing model from the issue text.