backport of commit 5bd8b89c19c71e19ad0a1abc9b35de9abb4d2cc3 (#18525)

Co-authored-by: Tim Gross <tgross@hashicorp.com>

.changelog/18524.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+template: reduce memory usage associated with communicating with the Nomad API
+```

helper/bufconndialer/bufconndialer.go

@@ -24,7 +24,10 @@ type BufConnWrapper struct {
 // New returns a new BufConnWrapper with a new bufconn.Listener. The wrapper
 // provides a dialer for creating connections to the listener.
 func New() (net.Listener, *BufConnWrapper) {
-	ln := bufconn.Listen(1024 * 1024)
+	// this buffer is sized to accept a maximum-sized Nomad Variable payload
+	// (64k) with plenty of room to spare for the metadata and envelope, in a
+	// single read
+	ln := bufconn.Listen(1024 * 100)
 	return ln, &BufConnWrapper{listener: ln}
 }