Switch vizierapi over to use bytes instead of string for StringColumn

Summary:
Fixes #552: GRPC C clients reject parsing string values from the serialized format
if the string is not valid UTF-8. The string and bytes pb types both serialize to bytes
over the wire, so we didn't detect this issue until someone requested http body data that contained
a bytes stream.

Fortunately the fix isn't difficult because string and bytes share the same wire format. Old clients
will remain backwards compatible with the current changes.

Also internally we already treat this data as bytes so conceptually not a large switch.

Test Plan:
1. Old client + new vizier still works as expected when all strings are utf-8 compatible.
2. New client + old vizier now avoids the issue highlighted in #552 when Pixie sends bytes data
3. New client + new vizier also avoids the issue and works fine.

Reviewers: jamesbartlett, zasgar, michelle, vihang, nlanam

Reviewed By: vihang, nlanam

Subscribers: nlanam

Signed-off-by: Phillip Kuznetsov <[email protected]>

Differential Revision: https://phab.corp.pixielabs.ai/D12069

GitOrigin-RevId: 73b4698d764af8a2f3834ae635a195cfe9a18cb6

proto/vizierpb/vizierapi.proto

@@ -144,7 +144,7 @@ message Time64NSColumn {
 
 // String data column.
 message StringColumn {
-  repeated string data = 1;
+  repeated bytes data = 1;
 }
 
 // A single column of data.

results.go

@@ -313,7 +313,7 @@ func extractDataFromCol(colData []*vizierpb.Column, rowIdx, colIdx int64, row []
 		if !ok {
 			return errdefs.ErrInternalMismatchedType
 		}
-		dCasted.ScanString(colTyped.StringData.Data[rowIdx])
+		dCasted.ScanString(string(colTyped.StringData.Data[rowIdx]))
 	case *vizierpb.Column_Uint128Data:
 		dCasted, ok := row[colIdx].(*types.UInt128Value)
 		if !ok {

results_test.go

@@ -87,10 +87,14 @@ func makeInt64Column(data []int64) *vizierpb.Column {
 }
 
 func makeStringColumn(data []string) *vizierpb.Column {
+	b := make([][]byte, len(data))
+	for i, d := range data {
+		b[i] = []byte(d)
+	}
 	return &vizierpb.Column{
 		ColData: &vizierpb.Column_StringData{
 			StringData: &vizierpb.StringColumn{
-				Data: data,
+				Data: b,
 			},
 		},
 	}