nsqd: /info api should return more configuration metadata

[ctlove0523]

run one nsqd instance on the localhost with default config,current /info api returns looks like below：

{
    "version": "1.2.1",
    "broadcast_address": "DESKTOP-TJTHRU9",
    "hostname": "DESKTOP-TJTHRU9",
    "http_port": 4151,
    "tcp_port": 4150,
    "start_time": 1650760244
}

but this information not enough for client to connect to nsqd instance,for example when client use tcp protocol connect nsqd and then send IDENTIFY command,client may want to configure heartbeat_interval、output_buffer_size、output_buffer_timeout and deflate_level,the maximum value of these four configurations controlled by nsqd config：

1、heartbeat_interval value range [1000,configured_max] --max-heartbeat-interval flag controls the configured_max value
2、output_buffer_size value range [64,configured_max] --max-output-buffer-size flag controls the configured_max value
3、output_buffer_timeout  value range [1ms,configured_max] --max-output-buffer-timeout flag controls the configured_max value and default is 250ms
4、deflate_level  value range [1,configured_max] --max-deflate-level flag controls the configured_max value

so if /info api can return these four configurations value is helpful,api returns may looks like below：

{
    "version":"1.2.1",
    "broadcast_address":"DESKTOP-TJTHRU9",
    "hostname":"DESKTOP-TJTHRU9",
    "http_port":4151,
    "tcp_port":4150,
    "start_time":1650760244,
    "max_heartbeat_interval":80000,
    "max_output_buffer_size":128,
    "max_output_buffer_timeout":500,
    "max_deflate_level":100
}

[mreiferson]

This seems like a reasonable idea.

[ploxiln]

looks like this was done in #1403