* go: replace objAPI-generated Pack func with method
See discussion at https://github.com/google/flatbuffers/issues/5668
* go: replace generated union type UnPack func with method
Similar to discussion https://github.com/google/flatbuffers/issues/5668
But signature:
```
func AnyUnPack(t Any, table flatbuffers.Table) *AnyT
```
Becomes,
```
func (rcv Any) UnPack(table flatbuffers.Table) *AnyT
```
As recommended by https://golang.org/pkg/cmd/go/internal/generate/:
To convey to humans and machine tools that code is generated,
generated source should have a line early in the file that
matches the following regular expression (in Go syntax):
^// Code generated .* DO NOT EDIT\.$
Similar to what protobufs does with its `Message` interface, introduce here such interface and create a generic `GetRootAs` method to deserialize a flatbuffer.
(Java doesn't support unsigned types).
ubyte/ushort return as int
uint returns as long
(all with correct masking)
ulong still returns as long, as before.
Tested: on Linux & Windows.
Bug 17521464
Change-Id: Id6bc8f38fc8c1a2f4e6733c6980dc6b6e322b452
Also fixed Go unit tests not being up to date with recent schema
changes.
Change-Id: I42e619f9c5ea05f6f937c68a5c8a92462c46bce3
Tested: on Linux and Windows.
