chore: Remove unused Ibis Python to JS UDF compiler (#2521)

The Python to JavaScript compiler previously vendored from ibis and
located at `third_party/bigframes_vendored/ibis/backends/bigquery/udf`
was unused in the production codebase and not supported by the vendored
backend. This PR removes the `udf/` directory and any references to
`PythonToJavaScriptTranslator` and `_get_udf_source` from
`third_party/bigframes_vendored/ibis/backends/bigquery/__init__.py`.

---
*PR created automatically by Jules for task
[17001767655361890847](https://jules.google.com/task/17001767655361890847)
started by @tswast*

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: tswast <247555+tswast@users.noreply.github.com>

Author: tswast

third_party/bigframes_vendored/ibis/backends/bigquery/__init__.py

@@ -21,9 +21,6 @@
     schema_from_bigquery_table,
 )
 from bigframes_vendored.ibis.backends.bigquery.datatypes import BigQuerySchema
-from bigframes_vendored.ibis.backends.bigquery.udf.core import (
-    PythonToJavaScriptTranslator,
-)
 from bigframes_vendored.ibis.backends.sql import SQLBackend
 from bigframes_vendored.ibis.backends.sql.compilers import BigQueryCompiler
 from bigframes_vendored.ibis.backends.sql.datatypes import BigQueryType
@@ -731,15 +728,7 @@ def compile(
     ):
         """Compile an Ibis expression to a SQL string."""
         query = self._to_sqlglot(expr, limit=limit, params=params, **kwargs)
-        udf_sources = []
-        for udf_node in expr.op().find(ops.ScalarUDF):
-            compile_func = getattr(
-                self, f"_compile_{udf_node.__input_type__.name.lower()}_udf"
-            )
-            if sql := compile_func(udf_node):
-                udf_sources.append(sql.sql(self.name, pretty=True))
-
-        sql = ";\n".join([*udf_sources, query.sql(dialect=self.name, pretty=True)])
+        sql = query.sql(dialect=self.name, pretty=True)
         self._log(sql)
         return sql
 
@@ -1186,68 +1175,6 @@ def _clean_up_cached_table(self, name):
             force=True,
         )
 
-    def _get_udf_source(self, udf_node: ops.ScalarUDF):
-        name = type(udf_node).__name__
-        type_mapper = self.compiler.udf_type_mapper
-
-        body = PythonToJavaScriptTranslator(udf_node.__func__).compile()
-        config = udf_node.__config__
-        libraries = config.get("libraries", [])
-
-        signature = [
-            sge.ColumnDef(
-                this=sg.to_identifier(name, quoted=self.compiler.quoted),
-                kind=type_mapper.from_ibis(param.annotation.pattern.dtype),
-            )
-            for name, param in udf_node.__signature__.parameters.items()
-        ]
-
-        lines = ['"""']
-
-        if config.get("strict", True):
-            lines.append('"use strict";')
-
-        lines += [
-            body,
-            "",
-            f"return {udf_node.__func_name__}({', '.join(udf_node.argnames)});",
-            '"""',
-        ]
-
-        func = sge.Create(
-            kind="FUNCTION",
-            this=sge.UserDefinedFunction(
-                this=sg.to_identifier(name), expressions=signature, wrapped=True
-            ),
-            # not exactly what I had in mind, but it works
-            #
-            # quoting is too simplistic to handle multiline strings
-            expression=sge.Var(this="\n".join(lines)),
-            exists=False,
-            properties=sge.Properties(
-                expressions=[
-                    sge.TemporaryProperty(),
-                    sge.ReturnsProperty(this=type_mapper.from_ibis(udf_node.dtype)),
-                    sge.StabilityProperty(
-                        this="IMMUTABLE" if config.get("determinism") else "VOLATILE"
-                    ),
-                    sge.LanguageProperty(this=sg.to_identifier("js")),
-                ]
-                + [
-                    sge.Property(
-                        this=sg.to_identifier("library"),
-                        value=self.compiler.f.array(*libraries),
-                    )
-                ]
-                * bool(libraries)
-            ),
-        )
-
-        return func
-
-    def _compile_python_udf(self, udf_node: ops.ScalarUDF) -> None:
-        return self._get_udf_source(udf_node)
-
     def _register_udfs(self, expr: ir.Expr) -> None:
         """No op because UDFs made with CREATE TEMPORARY FUNCTION must be followed by a query."""