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GH-43837: [Go][IPC] Consolidate StreamWriter and FileWriter, ensuring that EOS indicator is written in file (#43890)



### Rationale for this change

Fixes: #43837

Much of the logic between the ipc stream writer and the file writer was split. This PR changes the file writer so that it uses a stream writer internally, ensuring that a valid stream is embedded within the file.

**TODO**
- [x] Remove @ bkietz's commits

### What changes are included in this PR?

- Refactor `fileWriter` to embed `streamWriter` and defer relevant methods
- Add test

### Are these changes tested?

Yes

### Are there any user-facing changes?

Go-generated IPC files will contain the EOS indicator

* GitHub Issue: #43837

Authored-by: Joel Lubinitsky <joellubi@gmail.com>
Signed-off-by: Joel Lubinitsky <joellubi@gmail.com>