Detailed docs on Socket.Read* and NetworkStream.Receive* return values

[antonfirsov]

The wording is mostly borrowed from the Stream.Read* variants but saying the peer socket performed a graceful shutdown instead of end of the stream has been reached, which describes the EOF reason more specifically in this case.

Fixes #10925.

[learn-build-service-prod]

Learn Build status updates of commit 424c7cb:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System.Net.Sockets/NetworkStream.xml	✅Succeeded	View
xml/System.Net.Sockets/Socket.xml	✅Succeeded	View

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[rzikm]

LGTM, modulo existing comments

[learn-build-service-prod]

Learn Build status updates of commit 963bf8e:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System.Net.Sockets/NetworkStream.xml	✅Succeeded	View
xml/System.Net.Sockets/Socket.xml	✅Succeeded	View

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel