refactor(expression): take the segments of a Java type name as varargs

[joaodinissf]

Why the change

Follows up on Ruben's suggestion in #1556: three of the four callers of javaName split a string into an array and wrapped it in a list only to pass it on, so the method now takes the segments as varargs.

Special things to note

• The fourth caller, addExpressionTypeNames, starts from the identifier's List<String> and converts it with toArray(String[]::new).
• No behaviour change; the fix(export,scope): record the Java types a model names as dependencies #1556 tests cover all four paths.
• After 19.3.0 is released, xtext.expression, xtext.export and xtext.scope need a version bump for the release version check, since their content changes against that baseline.

Change outline

 xtext.expression/.../AbstractExpressionModelResourceDescriptionManager.java
-  javaName(final List<String> segments)      segments.stream()
+  javaName(final String... segments)         Arrays.stream(segments)
 xtext.export/.../ExportResourceDescriptionManager.java   javaName(List.of(x.split("::")))  → javaName(x.split("::"))
 xtext.scope/.../ScopeResourceDescriptionManager.java     same, for extensions and inject types

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