feat(spanner/spannertest): add support for bool parameter types (#2674)

I tested this against my own codebase as well and it resolved the issue for both my code as well as the integration tests. Previously this would fail with:

```
spanner: code = "Unknown", desc = "rpc error: code = Unknown desc = unsupported well-known type value kind *structpb.Value_BoolValue"
```

spanner/spannertest/db_eval.go

@@ -656,6 +656,7 @@ func compareVals(x, y interface{}) int {
 }
 
 var (
+	boolType    = spansql.Type{Base: spansql.Bool}
 	int64Type   = spansql.Type{Base: spansql.Int64}
 	float64Type = spansql.Type{Base: spansql.Float64}
 	stringType  = spansql.Type{Base: spansql.String}
@@ -664,6 +665,8 @@ var (
 func (ec evalContext) colInfo(e spansql.Expr) (colInfo, error) {
 	// TODO: more types
 	switch e := e.(type) {
+	case spansql.BoolLiteral:
+		return colInfo{Type: boolType}, nil
 	case spansql.IntegerLiteral:
 		return colInfo{Type: int64Type}, nil
 	case spansql.StringLiteral:

spanner/spannertest/db_test.go

@@ -526,6 +526,13 @@ func TestTableData(t *testing.T) {
 				{"Sam"},
 			},
 		},
+		{
+			`SELECT MAX(Name) FROM Staff WHERE Cool = @p1 LIMIT 1`,
+			queryParams{"p1": boolParam(true)},
+			[][]interface{}{
+				{"Teal'c"},
+			},
+		},
 		{
 			`SELECT MIN(Name) FROM Staff`,
 			nil,
@@ -881,6 +888,7 @@ func floatV(f float64) *structpb.Value                { return &structpb.Value{K
 func boolV(b bool) *structpb.Value                    { return &structpb.Value{Kind: &structpb.Value_BoolValue{b}} }
 func nullV() *structpb.Value                          { return &structpb.Value{Kind: &structpb.Value_NullValue{}} }
 
+func boolParam(b bool) queryParam     { return queryParam{Value: b, Type: boolType} }
 func stringParam(s string) queryParam { return queryParam{Value: s, Type: stringType} }
 func intParam(i int64) queryParam     { return queryParam{Value: i, Type: int64Type} }
 func floatParam(f float64) queryParam { return queryParam{Value: f, Type: float64Type} }

spanner/spannertest/inmem.go

@@ -761,6 +761,8 @@ func parseQueryParam(v *structpb.Value, typ *spannerpb.Type) (queryParam, error)
 		return queryParam{}, fmt.Errorf("unsupported well-known type value kind %T", v)
 	case *structpb.Value_NullValue:
 		return queryParam{Value: nil}, nil // TODO: set a type?
+	case *structpb.Value_BoolValue:
+		return queryParam{Value: v.BoolValue, Type: boolType}, nil
 	case *structpb.Value_NumberValue:
 		return queryParam{Value: v.NumberValue, Type: float64Type}, nil
 	case *structpb.Value_StringValue: