Fix the NMEA checksum offset and harden the buffer writes around it (#11293)

* Checksum NMEA sentences from the $ delimiter

The PositionLite printWPL() format begins with a CRLF, so the fixed start offset of 1 folded the newline and the $ into the checksum and every sentence went out with a wrong value. Locate the $ instead and stop at the terminator or a \*.

* Clamp truncated writes and harden the remaining fixed buffers

snprintf returns the length it would have written, so a truncated NMEA sentence
made buf + len point past the buffer and bufsz - len underflow into a huge size
for the checksum append. Clamp after each write.

Also pulls in the rest of #11236: the two remaining Dropzone sprintf calls, the
dead strcpy in mt_sprintf that wrote one byte past a zero-size allocation for an
empty format, and the 10-byte errcode buffer that INT32_MIN overflows.

Co-Authored-By: Andrew Yong <me@ndoo.sg>

* Bail out on a zero-sized buffer and cast err for %ld

snprintf writes nothing at all when bufsz is 0, not even a terminator, so the
checksum helper would run strchr over whatever the buffer already held. Return
before touching it.

int32_t is not long on every target, so cast before formatting with %ld.

Co-Authored-By: Andrew Yong <me@ndoo.sg>

* Add NMEA sentence regression tests

Covers checksum computation from the $ delimiter for both printWPL
overloads and printGGA, zero-sized buffers, and truncated buffers down
to one byte.

Co-Authored-By: Andrew Yong <me@ndoo.sg>

* Tighten checksum parsing and pin the WPL fixture checksum

Require exactly two hex digits followed by the sentence terminator, and
assert both WPL overloads against a known checksum instead of comparing
them to each other.

* Bump native suite count to 43

---------

Co-authored-by: Andrew Yong <me@ndoo.sg>

src/modules/DropzoneModule.cpp

@@ -82,11 +82,11 @@ meshtastic_MeshPacket *DropzoneModule::sendConditions()
         auto windDirection = telemetry.variant.environment_metrics.wind_direction;
         auto temp = telemetry.variant.environment_metrics.temperature;
         auto baro = UnitConversions::HectoPascalToInchesOfMercury(telemetry.variant.environment_metrics.barometric_pressure);
-        sprintf(replyStr, "%s @ %02d:%02d:%02dz\nWind %.2f kts @ %d°\nBaro %.2f inHg %.2f°C", dropzoneStatus, hour, min, sec,
-                windSpeed, windDirection, baro, temp);
+        snprintf(replyStr, sizeof(replyStr), "%s @ %02d:%02d:%02dz\nWind %.2f kts @ %d°\nBaro %.2f inHg %.2f°C", dropzoneStatus,
+                 hour, min, sec, windSpeed, windDirection, baro, temp);
     } else {
         LOG_ERROR("No sensor found");
-        sprintf(replyStr, "%s @ %02d:%02d:%02d\nNo sensor found", dropzoneStatus, hour, min, sec);
+        snprintf(replyStr, sizeof(replyStr), "%s @ %02d:%02d:%02d\nNo sensor found", dropzoneStatus, hour, min, sec);
     }
     LOG_DEBUG("Conditions reply: %s", replyStr);
     reply->decoded.payload.size = strlen(replyStr); // You must specify how many bytes are in the reply