Max feed count per sketch

- Arduino board: **Adafruit Feather HUZZAH with ESP8266**

- Arduino IDE version (found in Arduino -> About Arduino menu): **1.8.13**

- List the steps to reproduce the problem below (if possible attach a sketch or
copy the sketch code in too):

**Configure 20+ AdafruitIO_Feeds**. I'm not sure if there is any correlation between the number of feeds configured for sub vs pub vs pub/sub.

The number of feeds that produces the exception seems relatively constant for me at 20+. However, the reason I found the issue was general, inconsistent lock-ups (that may be completely unrelated).

The sketch I am using to reproduce the error is below. The only information in config.h is my WiFi and AIO authentication information.

```
#include "config.h" // Needed for Adafruit IO
#include "AdafruitIO_WiFi.h"

#if defined(USE_AIRLIFT) || defined(ADAFRUIT_METRO_M4_AIRLIFT_LITE) || \
defined(ADAFRUIT_PYPORTAL)
// Configure the pins used for the ESP32 connection
#if !defined(SPIWIFI_SS) // if the wifi definition isnt in the board variant
// Don't change the names of these #define's! they match the variant ones
#define SPIWIFI SPI
#define SPIWIFI_SS 10 // Chip select pin
#define SPIWIFI_ACK 9 // a.k.a BUSY or READY pin
#define ESP32_RESETN 6 // Reset pin
#define ESP32_GPIO0 -1 // Not connected
#endif
AdafruitIO_WiFi io(IO_USERNAME, IO_KEY, WIFI_SSID, WIFI_PASS, SPIWIFI_SS,
SPIWIFI_ACK, ESP32_RESETN, ESP32_GPIO0, &SPIWIFI);
#else
AdafruitIO_WiFi io(IO_USERNAME, IO_KEY, WIFI_SSID, WIFI_PASS);
#endif

//For Adafruit IO
AdafruitIO_Time *seconds = io.time(AIO_TIME_SECONDS);
AdafruitIO_Feed *nightmodeButtonFeed = io.feed("alarm.nightmode");
AdafruitIO_Feed *debugButtonFeed = io.feed("alarm.debug-button");

//AdafruitIO_Feed *currentTempFeed = io.feed("air-particulate-sensor.currenttemp");
//AdafruitIO_Feed *currentHumiFeed = io.feed("air-particulate-sensor.currenthumi");
//AdafruitIO_Feed *currentSmokeFeed = io.feed("air-particulate-sensor.currentsmoke");
//AdafruitIO_Feed *pm25CurrentFeed = io.feed("air-particulate-sensor.currentpm25");
AdafruitIO_Feed *pm10CurrentFeed = io.feed("air-particulate-sensor.currentpm10");
AdafruitIO_Feed *pm25AQIFeed = io.feed("air-particulate-sensor.aqipm25");

AdafruitIO_Feed *pm10AQIFeed = io.feed("air-particulate-sensor.aqipm10");

//AdafruitIO_Feed *light = io.feed("light");
//AdafruitIO_Feed *counter = io.feed("counter");
AdafruitIO_Feed *pm25nowCastFeed = io.feed("air-particulate-sensor.nowcastpm25");
AdafruitIO_Feed *pm10nowCastFeed = io.feed("air-particulate-sensor.nowcastpm10");

AdafruitIO_Feed *NH3Feed = io.feed("kencana-air-sensor.nh3");
AdafruitIO_Feed *COFeed = io.feed("kencana-air-sensor.co");
AdafruitIO_Feed *NO2Feed = io.feed("kencana-air-sensor.no2");
AdafruitIO_Feed *NO2ppbvFeed = io.feed("kencana-air-sensor.no2-ppbv");
AdafruitIO_Feed *NO2HourlyAvgFeed = io.feed("kencana-air-sensor.no2-hrly-avg");
AdafruitIO_Feed *NO2HourlyMinFeed = io.feed("kencana-air-sensor.no2-hrly-min");
AdafruitIO_Feed *NO2HourlyMaxFeed = io.feed("kencana-air-sensor.no2-hrly-max");

AdafruitIO_Feed *C3H8Feed = io.feed("kencana-air-sensor.c3h8");
AdafruitIO_Feed *C4H10Feed = io.feed("kencana-air-sensor.c4h10");
AdafruitIO_Feed *CH4Feed = io.feed("kencana-air-sensor.ch4");
AdafruitIO_Feed *H2Feed = io.feed("kencana-air-sensor.h2");
AdafruitIO_Feed *C2H5OHFeed = io.feed("kencana-air-sensor.c2h5oh");

void setup()
{
Serial.begin(115200);
Serial.setDebugOutput(true);

io.connect();

//subscribe to AIO feeds from which we want input
//iso->onMessage(handleISO);
seconds->onMessage(handleSecs);
nightmodeButtonFeed->onMessage(handlenightmodeButtonFeed);
debugButtonFeed->onMessage(handledebugButtonFeed);

while(io.status() < AIO_CONNECTED) {
Serial.print(".");
delay(500);
}
}

void loop() {
io.run();
// put your main code here, to run repeatedly:
}
void handlenightmodeButtonFeed(AdafruitIO_Data *data)
{
}
void handledebugButtonFeed(AdafruitIO_Data *data)
{
}
void handlepingButtonFeed(AdafruitIO_Data *data)
{
}
void handleSecs(char *data, uint16_t len)
{
Serial.println(data);
}
```

The exception that I get from the ESP8266 is below:

> Exception 28: LoadProhibited: A load referenced a page mapped with an attribute that does not permit loads
> PC: 0x40220f96: br_ssl_hs_client_run at src/ssl/ssl_hs_client.c line 1871
> EXCVADDR: 0x00000e94
>
> Decoding stack results
> 0x402208e1: br_ssl_hs_client_run at src/ssl/ssl_hs_client.c line 1528
> 0x4021ef90: jump_handshake at src/ssl/ssl_engine.c line 1081
> 0x4021f475: br_ssl_engine_recvrec_ack at src/ssl/ssl_engine.c line 1206
> 0x40204ee2: BearSSL::WiFiClientSecure::_run_until(unsigned int, bool) at /Users/mwright/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.cpp line 540
> 0x402023ec: Adafruit_MQTT_Client::connectServer() at /Users/mwright/Documents/Arduino/libraries/Adafruit_MQTT_Library/Adafruit_MQTT_Client.cpp line 34
> 0x40205091: BearSSL::WiFiClientSecure::available() at /Users/mwright/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.cpp line 386
> 0x402044f2: BearSSL::WiFiClientSecure::connected() at /Users/mwright/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.cpp line 260
> 0x40203120: ESP8266WiFiSTAClass::status() at /Users/mwright/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/libraries/ESP8266WiFi/src/ESP8266WiFiSTA.cpp line 634
> 0x40208e48: Adafruit_MQTT_Client::connected() at /Users/mwright/Documents/Arduino/libraries/Adafruit_MQTT_Library/Adafruit_MQTT_Client.cpp line 48
> 0x40201524: AdafruitIO::mqttStatus(bool) at /Users/mwright/Documents/Arduino/libraries/Adafruit_IO_Arduino/src/AdafruitIO.cpp line 437
> 0x402015bf: AdafruitIO::status() at /Users/mwright/Documents/Arduino/libraries/Adafruit_IO_Arduino/src/AdafruitIO.cpp line 368
> 0x402010bd: setup() at /Users/mwright/Documents/Arduino/web_gateway/web_gateway.ino line 67
> 0x40207158: loop_wrapper() at /Users/mwright/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/cores/esp8266/core_esp8266_main.cpp line 194

Thank you in advance for your help!

Start with the reproducing sketch's io.feed declarations and setup() connection loop, then trace AdafruitIO::status() in src/AdafruitIO.cpp around line 368 alongside the reported Adafruit_MQTT and ESP8266 BearSSL stack frames. Reproduce with 20 or more feeds and determine the feed-count boundary and failure behavior; done means the limit or crash cause is identified and covered by a reliable regression test.

Written by the indexing model from the issue text.