unify error handling for FileStream and Pipe Streams

[adamsitnik]

This PR changes FileStream to match AnonymousPipe*Stream, NamedPipe*Stream edge case error handling. Namely:

• when the server pipe disconnects or gets closed, a write to the client FileStream fails with an exception rather than reporting success and writing nothing (what we had so far).
• when the server pipe disconnects, a read from FileStream returns zero rather than throwing an exception (what we had so far).

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Issue Details

---

TODO:

• Write methods
• Test exclusions for platforms that don't support pipes like Linux Bionic etc

Author:	adamsitnik
Assignees:	-
Labels:	area-System.IO
Milestone:	8.0.0

[stephentoub]

Nit:
I'm finding it very difficult to read and tell apart all of these different test names, including pulling out the salient details. Can you restructure them to a form something along the lines of:

AnonymousPipeServer_AnonymousPipeClient_ServerClosed_ReadReturnsZero
AnonymousPipeServer_FileStreamClient_ServerClosed_ReadReturnsZero
NamedPipeServer_FileStreamClient_ServerDisconnects_ReadReturnsZero
...

etc.?

[adamsitnik]

@stephentoub can we meet somewhere in the middle?

- WhenAnonymousPipeServerIsClosedAnonymousPipeClientReadReturnsZero
+ When_AnonymousPipeServer_IsClosed_AnonymousPipeClient_ReadReturnsZero

Since we are using the [Fact] to annotate the tests I am trying to name in the way that they describe the fact they are testing.

[stephentoub]

Thanks.

[adamsitnik]

The test failures are unrelated (#78017), merging.

[adamsitnik]

@stephentoub thank you for the review! We are one step closer to PipeStream and File Stream code unification (preferably reuse)