fix(ipv4): make() rejects a TS timestamp dict keyed by address strings #1402

Describe the bug
IPv4.make() rejects a TS option whose timestamp dict is keyed by address strings. _make_opt_ts calls int(ip) on each key at pcapkit/protocols/internet/ipv4.py:1655, and the .items(True) path at :1631 does the same, so a dotted-quad string raises instead of being parsed as an address. IPv4Address keys work.

To Reproduce
IPv4(options=[(OptionNumber.TS, {'timestamp': {'1.2.3.4': timedelta(milliseconds=1)}})], protocol=253) raises ValueError: invalid literal for int() with base 10: '1.2.3.4'. This reproduces on main, and also at #1399's head d04716c37, which leaves it unchanged.

Expected behavior
Address keys are converted with ipaddress.ip_address (rejecting bool, as the other address fields do), so a string key works like an IPv4Address key.

Found by the #1399 cross-review. Blocked until #1399 merges, because both PRs edit _make_opt_ts.