feat: add Sequence.all method and forall documentation with tests

Implement `all(f)` method on Sequence class that returns true if all elements pass the predicate function. Add corresponding documentation entry for `forall(predicate)` in core-library.markdown. Include three test files covering basic functionality, non-boolean return handling, and non-function argument error cases.

src/wren_core.c

@@ -57,6 +57,13 @@ static const char* libSource =
 "    }\n"
 "    return result\n"
 "  }\n"
+"\n"
+"  all(f) {\n"
+"    for (element in this) {\n"
+"      if (!f.call(element)) return false\n"
+"    }\n"
+"    return true\n"
+"  }\n"
 "}\n"
 "\n"
 "class List is Sequence {\n"