test: read and write shades.cfg and backups on the PC

The records move to ConfigRecords, free of the file system and the
shade model, with 33 unit tests: each record's size against the header,
a round trip of each, the layouts of versions 2 to 24, and a real backup
when CONFIG_BACKUP names one.

The tests found, and this fixes:
- A quoted value as long as its field (a hostname of 30 or more
  characters, a full NTP server, MQTT host or time zone) was read short,
  and every value after it shifted.
- A comma in a shade, group or room name shifted the rest of its record.
  Names are read at their fixed width.
- 4.0 boards without Ethernet declared the network record 28 bytes longer
  than they wrote it, so a restore of the radio without the network read
  the radio from the middle of its record.  Records are read and skipped
  to their newline, and backup() measures what it writes.
- A restore cleared rooms beyond the backup's only on load.

A restore now takes the backup's rolling codes even when they are lower
than NVS's; a load still keeps the higher.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ConfigSettings.cpp

@@ -226,36 +226,6 @@ void ConfigSettings::print() {
   if(this->connType == conn_types_t::ethernet || this->connType == conn_types_t::ethernetpref) this->Ethernet.print();
 #endif
 }
-uint16_t ConfigSettings::calcSettingsRecSize() {
-  return strlen(this->fwVersion.name) + 3 
-    + strlen(this->hostname) + 3
-    + strlen(this->NTP.ntpServer) + 3
-    + strlen(this->NTP.posixZone) + 3
-    + 6  // ssdpbroadcast
-    + 6; // updateCheck
-}
-uint16_t ConfigSettings::calcNetRecSize() {
-  return 4 // connType
-    + 6 // dhcp
-    + this->IP.ip.toString().length() + 3
-    + this->IP.gateway.toString().length() + 3
-    + this->IP.subnet.toString().length() + 3
-    + this->IP.dns1.toString().length() + 3
-    + this->IP.dns2.toString().length() + 3
-    + strlen(this->MQTT.protocol) + 3
-    + strlen(this->MQTT.hostname) + 3
-    + 6 // MQTT Port
-    + 6 // PubDisco
-    + strlen(this->MQTT.rootTopic) + 3
-    + strlen(this->MQTT.discoTopic) + 3
-    + 4 // ETH.boardType
-    + 4 // ETH.phyType
-    + 4 // ETH.clkMode
-    + 5 // ETH.phyAddress
-    + 5 // ETH.PWRPin
-    + 5 // ETH.MDCPin
-    + 5; // ETH.MDIOPin
-}
 bool MQTTSettings::begin() {
   this->load();
   return true;