APP_CONTEXT_DEPS_FILES points to non-existing file in single-file bundle

[vitek-karas]

When running an app as .NET 5 single-file bundle, the AppContext.GetData("APP_CONTEXT_DEPS_FILES") points to a non-existing file - <directory with the bundle>/myapp.deps.json.
The runtime property should return empty-string for self-contained single-file and should return only framework deps files for framework-dependent single-file.

For .NET 6 we should consider adding some way to actually reading the content of the application's .deps.json file which is currently not accessible in any way.

[ghost]

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[vitek-karas]

Repro is now included in my single-file test app: https://github.com/vitek-karas/single-file-feature-test/blob/17d579bff6d67d11e8391dc7df120021dd3e85ff/FeatureTest/RuntimeProperties.cs#L24