fix: risingwave struct field access

Add a specific visit method for visit_StructField.
"f{idx}" is not supported like in Postgres.
Use dot and parenthesis annotation as dots only is not working on the first level.

`dataframe.metadata["user.profile.link"].value.url``

Will be translated to:

`(((("t1"."metadata")."user.profile.link").value).url)``

Resolves #11182

Author: Christophe Di Prima

ibis/backends/sql/compilers/risingwave.py

@@ -193,5 +193,8 @@ def visit_MapContains(self, op, *, arg, key):
             self.cast(arg, op.arg.dtype), self.cast(key, op.key.dtype)
         )
 
+    def visit_StructField(self, op, *, arg, field):
+        return sge.Dot(this=sge.Paren(this=arg), expression=sge.to_identifier(field))
+
 
 compiler = RisingWaveCompiler()