Modify dartdev language-server to call the server snapshot
Modify dartdev language-server to call the server snapshot

This change also modifies the Dart Analysis Server to default to use the LSP protocol

Change-Id: I73a1ceae9a05bc8e5af219e4f28df959c054d4c9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/247461
Commit-Queue: Jaime Wren <cd1ab83d11dd618c6b8cd01592020d0bd5183fdc@google.com>
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk