Default EnableUnsafeBinaryFormatterSerialization and EnableUnsafeUTF7Encoding in trimmed applications

[eerhardt]

Fix #14475

FYI - @jkotas

[ghost]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[pgovind]

Defaults look good to me.

[sbomer]

#14475 mentions that EnableUnsafeUTF7Encoding is already turned off by default, but I only see it turned off in the blazor SDK. Should that one be defaulted in the .NET SDK?

[eerhardt]

#14475 mentions that EnableUnsafeUTF7Encoding is already turned off by default, but I only see it turned off in the blazor SDK. Should that one be defaulted in the .NET SDK?

It's value is defaulted to false in the runtime if it isn't specified in the runtimeconfig.json. So there's really no reason to default again in the .NET SDK. There's no behavior difference, and all we get is an extra, unnecessary entry in the runtimeconfig.json.

The value we get out of this change (set it during PublishTrimmed=true) is that the linker sees its value, and trims away the UTF7 code in the runtime.