Fix SslStreamDisposeTest failures during parallel handshake

[rzikm]

Fixes #113834.

3 distinct types of test failures

• InvalidOperationException while writing to StreamBuffer - test implementation detail, replaced by real TCP streams
• ODE and other exceptions wrapped in AuthenticationException - I couldn't decide whether to fix this in product, but then discovered that there were also other failures where there were weird error codes from platform crypto layer, so ignoring AuthenticationExceptions seems better here.

[Copilot]

Pull Request Overview

The PR aims to address SslStreamDisposeTest failures by using real TCP streams and by improving exception handling during parallel handshakes.

• Replaced ConnectedSslStreams with real Tcp streams to avoid issues with concurrent disposal.
• Updated the using blocks to reflect the new stream instantiation.
• Expanded the exception catch logic to include AuthenticationException for more robust test validation.

Comments suppressed due to low confidence (2)

src/libraries/System.Net.Security/tests/FunctionalTests/SslStreamDisposeTest.cs:119

• [nitpick] Consider renaming the 'server' variable to 'serverSslStream' for clarity and consistency with the client SslStream variable.

using SslStream server = new SslStream(serverStream);

src/libraries/System.Net.Security/tests/FunctionalTests/SslStreamDisposeTest.cs:151

• Consider adding a dedicated test that simulates an AuthenticationException scenario to verify that this expected case is handled correctly.

catch (Exception ex) when (ex
                    is ObjectDisposedException // disposed locally
                    or IOException // disposed remotely (received unexpected EOF)
                    or AuthenticationException) // disposed wrapped in AuthenticationException or error from platform library

[rzikm]

/azp run runtime-libraries-coreclr outerloop

[wfurt]

while the platform noise is unpleased IMHO I feel it is OK since we may be breaking operations in-flight. We would probably need to check disposed flag on failure to see that the failure is result of Dispose and throw ODE instead.

[rzikm]

/azp run runtime-libraries-coreclr outerloop

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[rzikm]

all System.Net.Security.Tests pass, good to merge.