Support binary search for struct in cpp (#4245)

* Support binary search for struct in cpp

CreateVectorOfSortedStruct is provided for convenience.

* fix continuous-integration error

* add generated files

* compile Ability.cs in csharp test

* compile Ability.cs in csharp

* modify according to code review

tests/MyGame/Example/Ability.go

@@ -0,0 +1,41 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+package Example
+
+import (
+	flatbuffers "github.com/google/flatbuffers/go"
+)
+
+type Ability struct {
+	_tab flatbuffers.Struct
+}
+
+func (rcv *Ability) Init(buf []byte, i flatbuffers.UOffsetT) {
+	rcv._tab.Bytes = buf
+	rcv._tab.Pos = i
+}
+
+func (rcv *Ability) Table() flatbuffers.Table {
+	return rcv._tab.Table
+}
+
+func (rcv *Ability) Id() uint32 {
+	return rcv._tab.GetUint32(rcv._tab.Pos + flatbuffers.UOffsetT(0))
+}
+func (rcv *Ability) MutateId(n uint32) bool {
+	return rcv._tab.MutateUint32(rcv._tab.Pos+flatbuffers.UOffsetT(0), n)
+}
+
+func (rcv *Ability) Distance() uint32 {
+	return rcv._tab.GetUint32(rcv._tab.Pos + flatbuffers.UOffsetT(4))
+}
+func (rcv *Ability) MutateDistance(n uint32) bool {
+	return rcv._tab.MutateUint32(rcv._tab.Pos+flatbuffers.UOffsetT(4), n)
+}
+
+func CreateAbility(builder *flatbuffers.Builder, id uint32, distance uint32) flatbuffers.UOffsetT {
+	builder.Prep(4, 8)
+	builder.PrependUint32(distance)
+	builder.PrependUint32(id)
+	return builder.Offset()
+}