Extended folding ignoring single-expression if statements over multiple lines

The "extended folding" option that Jakub implemented ensures that the line with the closing `}` is present.

With single-expression `if`s, there is no closing `}` so it includes the last line of the statement to fold.
This issue only occurs if the `if` statement consists of multiple lines.

Reproducer (note the empty line after the `if(b)` and the missing `{}`s):
```java
package org.example.test;

public class Repro {

public String test(boolean b) {
if (b)

return "a";
return "b";
}

}
```
Expected result after collapsing the `if(b)`:
```java
package org.example.test;

public class Repro {

public String test(boolean b) {
if (b)
return "a";
return "b";
}

}
```
Actual result after collapsing the `if(b)`:
```java
package org.example.test;

public class Repro {

public String test(boolean b) {
if (b)

return "a";
return "b";
}

}
```

I think it's the same for other control structures.

@fedejeanne

The issue names no source files or tests. Start by reproducing the Java example with extended folding enabled, then locate the folding implementation and related tests; done means collapsing a multiline single-expression if removes the empty line while preserving the return statement, with other control structures checked if applicable.

Written by the indexing model from the issue text.