feat(bigquery): add timestamp diff support (#11944)

## Description of changes

Add timestamp diff support to bigquery.

## Issues closed

Resolves #11945

Author: ssabdb

ibis/backends/sql/compilers/bigquery/__init__.py

@@ -136,7 +136,6 @@ class BigQueryCompiler(SQLGlotCompiler):
         ops.Median,
         ops.RegexSplit,
         ops.RowID,
-        ops.TimestampDiff,
         ops.Kurtosis,
     )
 
@@ -390,6 +389,9 @@ def visit_TimestampDelta(self, op, *, left, right, part):
             "timestamp difference with mixed timezone/timezoneless values is not implemented"
         )
 
+    def visit_TimestampDiff(self, op, *, left, right):
+        return sge.TimestampDiff(this=left, expression=right, unit=self.v.SECOND)
+
     def visit_GroupConcat(self, op, *, arg, sep, where, order_by):
         if where is not None:
             arg = self.if_(where, arg, NULL)

ibis/backends/tests/test_generic.py

@@ -1118,7 +1118,7 @@ def test_interactive(alltypes, monkeypatch):
     expr = alltypes.mutate(
         str_col=_.string_col.replace("1", "").nullif("2"),
         date_col=_.timestamp_col.date(),
-        delta_col=lambda t: ibis.now() - t.timestamp_col,
+        delta_col=lambda t: ibis.now() - t.timestamp_col.cast("timestamp('UTC')"),
     )
 
     repr(expr)

ibis/backends/tests/test_temporal.py

@@ -835,7 +835,7 @@ def convert_to_offset(x):
             id="timestamp-subtract-timestamp",
             marks=[
                 pytest.mark.notimpl(
-                    ["bigquery", "snowflake", "sqlite", "exasol", "mssql"],
+                    ["snowflake", "sqlite", "exasol", "mssql"],
                     raises=com.OperationNotDefinedError,
                 ),
                 pytest.mark.notimpl(