Don't set PublishAot in SDK by default

[sbomer]

Opening this as an alternative to reverting the PublishAot changes in #74036.
The intention was to default PublishAot to true when using the package reference, not when using the ILCompiler that ships with the SDK. These props get imported on both paths - I think it was just missing a check.

[LakshanF]

Thanks!

[MichalStrehovsky]

/backport to release/7.0-rc1

[github-actions]

Started backporting to release/7.0-rc1: https://github.com/dotnet/runtime/actions/runs/2872323345

[sbomer]

I did some amount of validation locally on a selection of the SDK tests that were failing in dotnet/sdk#27149 and am seeing them pass with this change.

[radical]

/azp run runtime-wasm

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[radical]

Also, ILCompiler* sdk shouldn't be imported for browser-wasm.

[MichalStrehovsky]

Also, ILCompiler* sdk shouldn't be imported for browser-wasm.

Props files don't know what we're going to target because they're included before users csproj that has those details. WASM builds include Windows targeting-related-props files as well; it's fine. They're not supposed to have side effects like this bug had, just set up the environment in a user-overridable way.