Test packages with OATS

[martincostello]

Fixes #63

Changes

• Refactor the OATS tests to consume the built NuGet packages, rather than compiling the distribution from source.
• Avoid warning when installing OATS by disabling the Go cache.
• Bump Swashbuckle.AspNetCore to the latest release.
• Cherry-pick change from Update OpenTelemetry package versions #145 to avoid ArgumentException when using v4 of the AWS SDK.

Merge requirement checklist

• Unit tests added/updated
• CHANGELOG.md file updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[Copilot]

Pull Request Overview

This PR refactors OATS tests to consume built NuGet packages rather than building from source, updates dependencies, and adjusts CI to publish and download NuGet artifacts.

• Refactor ASP.NET Core example to conditionally use either a project reference or the built NuGet package based on BuildDistroFromSource.
• Bump Swashbuckle.AspNetCore from 8.1.4 to 9.0.3.
• Add NuGet.config and CI steps to build, publish, and consume local NuGet packages.
• Disable Go module caching during OATS installation and pass BuildDistroFromSource to Docker builds.
• Cherry-pick AWS SDK ArgumentException fix into AwsController.

Reviewed Changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
examples/net8.0/aspnetcore/aspnetcore.csproj	Bumped Swashbuckle, added conditional project vs. package reference ItemGroups
examples/net8.0/aspnetcore/Controllers/AwsController.cs	Added null-conditional check when selecting bucket names
docker/docker-compose-aspnetcore/docker-compose*.yml	Pass BuildDistroFromSource via build args in all relevant compose files
docker/docker-compose-aspnetcore/.dockerignore	Include .packages/ folder
NuGet.config	Configure local package source and mapping
.github/workflows/oats.yml	New package job builds NuGet artifacts, acceptance-tests job downloads them & disables Go cache

Comments suppressed due to low confidence (1)

examples/net8.0/aspnetcore/Controllers/AwsController.cs:20

• The empty array literal [] is not valid C# syntax. Use Array.Empty<string>() or new string[0] to return an empty string array.

        var buckets = response.Buckets?.Select(o => o.BucketName).ToArray() ?? [];