Improve AddRegisterBeforeSnapshot

[ppittle]

Increase the robustness of GetBeforeSnapshotRequests. Create a unique feature collection on every warmup call.

Issue #, if available:
#2069

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[normj]

Can you add the change file to the PR? Here is my stab at it but feel free to change it. Just be sure to include both Amazon.Lambda.AspNetCoreServer and Amazon.Lambda.AspNetCoreServer,Hosting in the change file.

{
  "Projects": [
    {
      "Name": "Amazon.Lambda.AspNetCoreServer",
      "Type": "Patch",
      "ChangelogMessages": [
        "Fixed issue when executing AddRegisterBeforeSnapshot callbacks to ensure each invocation has a new ASP.NET Core feature collection and HttpContext."
      ]
    },
    {
      "Name": "Amazon.Lambda.AspNetCoreServer.Hosting",
      "Type": "Patch",
      "ChangelogMessages": [
        "Update Amazon.Lambda.AspNetCoreServer dependency for latest patch fix."
      ]
    }
  ]
}

[ppittle]

Apologies, I forgot about the changelog message. Took @normj's messages verbatim :)

[GarrettBeatty]

ive updated the base branch to dev

[GarrettBeatty]

Rerunning tests with correct branch. https://github.com/aws/aws-lambda-dotnet/actions/runs/15049599772