[esp32] Preserve crash data across OTA rollback reboots

Don't clear the crash data magic marker at boot time. Previously,
crash_handler_read_and_clear() would clear the magic immediately,
so if OTA rollback triggered a reboot before an API client connected,
the crash trace was lost.

Now the magic is only cleared after crash_handler_log() delivers the
data to an API client via crash_handler_clear().

esphome/components/api/api_connection.h

@@ -276,6 +276,7 @@ class APIConnection final : public APIServerConnectionBase {
       App.schedule_dump_config();
 #ifdef USE_ESP32_CRASH_HANDLER
     esp32::crash_handler_log();
+    esp32::crash_handler_clear();
 #endif
 #ifdef USE_RP2040_CRASH_HANDLER
     rp2040::crash_handler_log();