Consider defaulting to `--suppress-fe-warnings` with `pub run`

[natebosch]

See discussion at #34137 (comment)

Assuming the default remains to print frontend warnings on startup we may want to alway suppress them with pub run and pub global run - including in the shell script created to execute the entrypoint without pub. The reasoning is that the user who activated a package and is running with pub is the least likely to be the developer and the least likely to be able to take action on the warnings.

As is this is an edge case - fe warnings only come in to play when running from source which is not the common pattern. dart-lang/pub#1683 would tip the scales though.

[sigurdm]

Is this still a thing?

In all cases pub run no longer exists. It is now dart run. Transferring to the sdk issue tracker.