Add optional addressBook output to begin() to capture discovered ROM addresses

[blah188]

Motivation

begin() already enumerates the bus (it searches and counts devices), but the discovered ROM addresses are dropped — they live only in a local variable. Callers that need the addresses must call getAddress(addr, index) afterwards, which runs a second SearchROM pass. On long or electrically marginal 1-Wire buses that second pass can intermittently fail (returns a zero / CRC-invalid ROM) even though begin()'s own search just succeeded — so a device that was counted can't be addressed.

Change

Add two optional, defaulted parameters:

void begin(uint8_t* addressBook = nullptr, uint8_t maxDeviceCount = 0);

When addressBook is provided, each valid ROM found during enumeration is copied into it (in discovery order, up to maxDeviceCount). This lets the caller reuse the addresses captured by the search that already ran, instead of re-discovering them with a second, less reliable search pass.

Backward compatibility

Fully backward compatible — with no arguments begin() behaves exactly as before (nothing is written). No change to any existing call site or behavior.

Example

DeviceAddress book[4];
sensors.begin(&book[0][0], 4);            // addresses captured during enumeration
uint8_t n = sensors.getDeviceCount();
float t = sensors.getTempC(book[0]);      // read by stored address, no re-search