The test `feature_addrman.py` currently serializes the addrdb without
specifying endianness for `int`s, so the machine's native byte order is used (see
https://docs.python.org/3/library/struct.html#byte-order-size-and-alignment)
and the generated `peers.dat` would be invalid on big-endian systems.
Fix this by explicitly specifying little-endian serialization via the
`<` character in `struct.pack(...)`.
fixes #24188
When downgrading, a peers.dat with a future version that has a minimum
required version larger than the downgraded version would cause an InitError.
This commit changes this behavior to overwrite the existing peers.dat with
a new empty one, while creating a backup in peers.dat.bak.
92617b7a75 effectively changed the
on-disk format in an incompatible way: old deserializers cannot
deal with multiple entries for the same IP.
Introduce a V4_MULTIPORT format, and increment the compatibility base,
so that old versions correctly recognize it as an incompatible future
version.
