TUN-5262: Allow to configure max fetch size for listing queries

This can be useful/important for accounts with many tunnels that exceed
the 1000 default page size.

There are various tunnel subcommands that use listing underneath, so we make
that flag a tunnel one, rather than adding it to each subcommand.

cmd/cloudflared/tunnel/cmd.go

@@ -646,6 +646,12 @@ func tunnelFlags(shouldHide bool) []cli.Flag {
 			Value:  "https://api.trycloudflare.com",
 			Hidden: true,
 		}),
+		&cli.UintFlag{
+			Name:    "max-fetch-size",
+			Usage:   `The maximum number of results that cloudflared can fetch from Cloudflare API for any listing operations needed`,
+			EnvVars: []string{"TUNNEL_MAX_FETCH_SIZE"},
+			Hidden:  true,
+		},
 		selectProtocolFlag,
 		overwriteDNSFlag,
 	}...)