Replace WebSocket exec/attach/port-forward transport with HTTP/2 duplex streaming

[Copilot]

The exec/attach/port-forward flows should no longer rely on WebSockets; they now use HTTP/2 streaming instead.

• Transport: Added an HTTP/2 duplex stream + Http2WebSocket wrapper and routed exec/attach/port-forward helpers through it, carrying subprotocol via X-Stream-Protocol-Version.
• Buffering: Implemented pooled producer/consumer buffering with safe lifecycle management and graceful close semantics.
• API surface/tests: Updated exec/attach/port-forward URIs to HTTP/2, skipped legacy WebSocket-only coverage, and refreshed expectations in unit tests.

Example (exec now uses HTTP/2 POST instead of ws://):

var ws = await client.WebSocketNamespacedPodExecAsync(
    "mypod", "mynamespace",
    new[] { "/bin/bash", "-c", "echo hi" },
    container: "mycontainer",
    webSocketSubProtocol: "v4.channel.k8s.io");

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• crl.comodoca.com
  • Triggering command: /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/.dotnet/dotnet /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/.dotnet/dotnet restore --no-dependencies /home/REDACTED/work/csharp/csharp/src/KubernetesClient.Classic/KubernetesClient.Classic.csproj --packages /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot git conf�� ernetesClient.AoINVALID,NEW --global tnet/tools/git user.name (dns block)
• ocsp.comodoca.com
  • Triggering command: /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/.dotnet/dotnet /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/.dotnet/dotnet restore --no-dependencies /home/REDACTED/work/csharp/csharp/src/KubernetesClient.Classic/KubernetesClient.Classic.csproj --packages /home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/csharp/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot git conf�� ernetesClient.AoINVALID,NEW --global tnet/tools/git user.name (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

fully remove websocket, using http2 instead

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[k8s-ci-robot]

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