Use integer division in encode_phys to prevent rounding errors with int64

[yves-chevallier]

While testing int64 values with SDOs, I observed an unexpected behavior:

>>> value = 0x55554444AAAABBBB
>>> d.node.sdo[16384][4].phys = value
>>> hex(d.node.sdo[16384][4].phys)
'0x55554444aaaabc00'

Upon investigation, it appears that the issue originates from the encode_phys function:

>>> value = 0x55554444AAAABBBB
>>> sdo.od.factor
1
>>> hex(sdo.od.encode_phys(value))
'0x55554444aaaabc00'

The problem lies in the fact that the division is performed using floating-point arithmetic rather than integer arithmetic, leading to rounding that causes a loss of up to 10 bits of precision.

def encode_phys(self, value: Union[int, bool, float, str, bytes]) -> int:
    if self.data_type in INTEGER_TYPES:
        value /= self.factor
        value = int(round(value))
    return value

To address this, we should detect whether the input value is an integer and, if so, perform integer division (//) instead of floating-point division. Additionally, it may be prudent to emit a warning when factor is not an integer, as this could lead to precision loss.