[release/8.0-staging] Stop building AppHost in native AOT testing

[ilonatommy]

Customer Impact

• Customer reported
• Found internally

Backport of #101270. Fixes #99423 - OOM failures in NativeAOT lanes. This is purely test infra change, so I am adding approved label directly.

Regression

• Yes
• No

Testing

CI.

Risk

Low, it's not a production-code change.

@MichalStrehovsky, this backport might be not enough and backporting #98939 might be needed as well. I did not include both changes at once due to your comment "We don't need to run analyzers on native AOT legs because they run on the same code elsewhere" - I have no idea if this is true for net8 as well. If you'd confirm it is save to backport, I am in favor of doing both to save the CI time.

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[ilonatommy]

It fails with #79575 because we're missing backport to sdk (dotnet/sdk#38644).

[jkotas]

Building apphost should not meaningfully contribute to the memory footprint of the build. Could you please explain why you expect that this change is going to fix the OOMs reported in #99423 ?

[ilonatommy]

I expected that building less subsets takes less resources of the VM. Because OOM happens only on net8, I was looking for major changes to how we run the tests on net8 and net9. Dropping apphost is one, the other one is dropping analyzers (#98939). As in the description, I applied only the apphost related one, I had doubts if we can apply both.

[ilonatommy]

Close as risky to fully backport and not guaranteed to have the expected effect.