Updates all null safe dependencies to versions that allow 2.10 stable and 2.11 dev releases.

Also updates flutter_goldens and flutter_goldens_client to allow 2.11 dev.

[versions] update to latest source span and roll engine to  4b8477d11573d233e6791204191c0090f733b05d (#66136)

PR #65873 enabled DDS for non-web Flutter applications. This change
surfaced a bug where DDS would not send ServiceRegistered events to VM
service clients when they subscribed to the Service stream. This would
cause tools and tests that rely on these events (e.g., hot reload in
VSCode) to fail.

Fixes #66038.

Update to latest dwds, file-nullsafety, and process-nullsafety for #62886

Update prepare_package.dart to use the process_runner package instead having duplicate code. (#62710)

Updates the prepare_package.dart script to use the process_runner package (which is where the ProcessRunner implementation was moved to).

This reverts commit 5b3dc525.

This reverts commit 9f4499f4.