Make System.IO.Packaging test trim safe

[MichalStrehovsky]

The existing pattern doesn't get statically analyzed and is breaking outerloop testing.

[MichalStrehovsky]

/azp run runtime-nativeaot-outerloop

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[carlossanlop]

@MichalStrehovsky For my own education, can you please share the output of the error you were seeing? Or if you had an issue open to track it, even better (there's none in the description).

Also, we should merge this before the snap on Monday. Ah, it's test, not critical to merge by then.

[MichalStrehovsky]

@MichalStrehovsky For my own education, can you please share the output of the error you were seeing? Or if you had an issue open to track it, even better (there's none in the description).

It's a nullreferenceexception since either the GetType or GetMethod returned null. It's visible in #104516. I don't file issues for things like this because it's not worth the hassle.

[MichalStrehovsky]

/azp run runtime-nativeaot-outerloop

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Azure Pipelines successfully started running 1 pipeline(s).

[MichalStrehovsky]

/ba-g The reflection test failure on ARM64 was known and has been fixed since the CI ran. Not going to rerun CI for that.