Adapter: Default deployment name to "tmp-readyset"

Sets the deployment name to "tmp-readyset" if none is provided. It is
expected that most users trying out ReadySet will not care about setting
a deployment name.

Release-Note-Core: The deployment name is no longer a required argument
  for the ReadySet adapter or server, and now defaults to
  "tmp-readyset". Users should take care to set the same deployment ID
  for all nodes in a deployment.
Change-Id: I4b9873880695d078061656af0989e05a0af25df2
Reviewed-on: https://gerrit.readyset.name/c/readyset/+/5651
Reviewed-by: Luke Osborne <luke@readyset.io>
Tested-by: Buildkite CI

readyset-server/src/main.rs

@@ -78,8 +78,13 @@ struct Options {
     #[clap(long)]
     use_aws_external_address: bool,
 
-    /// ReadySet deployment ID.
-    #[clap(long, env = "DEPLOYMENT", value_parser = NonEmptyStringValueParser::new())]
+    /// ReadySet deployment ID. All nodes in a deployment must have the same deployment ID.
+    #[clap(
+        long,
+        env = "DEPLOYMENT",
+        default_value = "tmp-readyset",
+        value_parser = NonEmptyStringValueParser::new()
+    )]
     deployment: String,
 
     /// The authority to use

readyset/src/lib.rs

@@ -155,8 +155,8 @@ pub struct Options {
     #[clap(long, short = 'a', env = "LISTEN_ADDRESS")]
     address: Option<SocketAddr>,
 
-    /// ReadySet deployment ID to attach to
-    #[clap(long, env = "DEPLOYMENT", value_parser = NonEmptyStringValueParser::new())]
+    /// ReadySet deployment ID. All nodes in a deployment must have the same deployment ID.
+    #[clap(long, env = "DEPLOYMENT", default_value = "tmp-readyset", value_parser = NonEmptyStringValueParser::new())]
     deployment: String,
 
     /// Database engine protocol to emulate. If omitted, will be inferred from the