[release/8.0-staging] Catch exception when subscribing to NetworkChange

[github-actions]

Backport of #94861 to release/8.0-staging

Fixes #94794

/cc @rzikm

Customer Impact

This is a regression against 7.0.
Customers impacted: Restricted environments like Google Cloud - customer reported in #94794

Whenever user sends any HTTP request (incl. HTTP 1.1 or 2.0) to a server which supports also HTTP/3 -- in specific constrained environments (like Google Cloud as reported in #94794), the user will NOT be able to read the response, because we will throw exception.

Workaround is to disable HTTP/3 via AppContext switch (or environment variable).

Customers would run into the same problem on 7.0, if they had msquic.so installed on the machine. That is not the case for customer reporting issue #94794 (they do not have msquic.so installed on their Google Cloud constrained environment).
When the msquic.so was NOT installed on 7.0, the problem didn't exist, but it DOES exist on 8.0 -- hence a regression. The reason is that the problematic check was delayed AFTER msquic.so presence check in 7.0. In 8.0 we changed the order to load msquic.so ONLY when user asks for HTTP/3 (see PR #83494), therefore doing the problematic check also for HTTP/1.1 and HTTP/2 requests, causing this regression.

Testing

Tested on simulated constrained environment (via injecting faults in Networking code). Tested both before and after change.

Risk

Low, change is only adding a catch block around code which throws only in constrained environments.

[ghost]

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Issue Details

---

Backport of #94861 to release/8.0-staging

/cc @rzikm

Customer Impact

Testing

Risk

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.Net.Http
Milestone:	-

[rzikm]

cc @karelz

[carlossanlop]

Today is code complete for the January Release. Please get this approved and merged by 4pm PT at the latest if you want this fix shipped there. Otherwise, this will have to wait for the February Release.
@rzikm @karelz

[karelz]

Thanks @carlossanlop, we are not ready yet. Let's aim for Feb. Thanks!

[karelz]

@artl93 this is ready for your approval - please mark it with Servicing-consider if you agree. Thanks!