Make sure otlphttp exporter tests include TraceID and SpanID (#4268)

Related to #4221

There was a report that TraceID and SpanID are correupted by otlphttp exporter.
I added to TraceID and SpanID to try to reproduce the bug. The bug is not reproduced
but keeping these in the test is useful.

internal/testdata/trace.go

@@ -101,6 +101,8 @@ func fillSpanOne(span pdata.Span) {
  span.SetStartTimestamp(TestSpanStartTimestamp)
  span.SetEndTimestamp(TestSpanEndTimestamp)
  span.SetDroppedAttributesCount(1)
+ span.SetTraceID(pdata.NewTraceID([16]byte{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10}))
+ span.SetSpanID(pdata.NewSpanID([8]byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18}))
  evs := span.Events()
  ev0 := evs.AppendEmpty()
  ev0.SetTimestamp(TestSpanEventTimestamp)