fix(mqtt): 8 KB MQTT task stack when TLS verifies a CA certificate

On boards with PSRAM the MQTT client runs in its own task with a 5120
byte stack. Verifying an EC certificate chain against a CA, such as
Let's Encrypt ISRG Root X2, needs about 6 KB, so the task overflowed
and the board boot looped on every connect.

The espMqttClient constructors now take the stack size, and
startClient() passes EMSESP_MQTT_STACKSIZE_CA (8192) when TLS is on
with a CA, keeping the 5120 default for insecure TLS and plain MQTT.
The client is recreated when that changes. The stack usage log
reports against the size the task was created with.

CHANGELOG_LATEST.md

@@ -71,6 +71,7 @@ This release is based on the latest Espressif/Arduino core version 3. It brings
 - a second boiler monitor `0xE4` carrying `0xFFFF` cleared a valid `pc0Flow`. That empty value is now ignored [#3224](https://github.com/emsesp/EMS-ESP32/issues/3224)
 - writing a negative custom entity value was always 1 too high because float-to-int rounding always added +0.5. Negative values now round the same way as positive ones [#3297](https://github.com/emsesp/EMS-ESP32/issues/3297)
 - after a cold boot, SoftAP fallback no longer abandons STA forever. If a home WiFi SSID is configured, EMS-ESP keeps retrying STA while the captive portal is up so a late-booting router (e.g. after a power outage) can still be joined; SoftAP stops once STA gets an IP
+- MQTT with TLS and a CA certificate crashed on every connect (a boot loop) on boards with PSRAM when the broker's certificate chain is EC, such as Let's Encrypt ISRG Root X2: verifying it needs about 6 KB of stack and the MQTT task only had 5120 bytes. The MQTT task now gets an 8 KB stack when TLS verifies a CA certificate, and keeps 5120 bytes for insecure TLS and plain MQTT
 
 ## Changed