Fix overflow for permanent peer address TTL

[alienx5499]

Summary

Fix undefined behaviour in InmemAddressRepository::calculateExpirationTime when using peer::ttl::kPermanent by mapping permanent TTLs directly to Clock::time_point::max() and adding a regression test.

Details

• Issue: Signed overflow in InmemAddressRepository::upsertAddresses (GitHub issue #281).
• Root cause: calculateExpirationTime used max_time - ttl and now + ttl; for ttl::kPermanent == std::chrono::milliseconds::max() both operations can overflow the underlying duration type and trigger UBSAN.
• Fix:
  • Special‑case ttl::kPermanent in calculateExpirationTime and immediately return Clock::time_point::max().
  • Keep the previous logic (now >= max_time - ttl ? max_time : now + ttl) for all other TTL values.

Tests

• New regression test: InmemAddressRepository_Test.PermanentTtlNoOverflow in test/libp2p/peer/address_repository/inmem_address_repository_test.cpp, which:
  • Inserts addresses with ttl::kPermanent via addAddresses and upsertAddresses.
  • Verifies they remain after collectGarbage() (permanent TTL addresses should never expire).
• Additional boundary test: InmemAddressRepository_Test.LargeTtlClampedToMax, which:
  • Uses a TTL very close to Milliseconds::max() and ensures the address remains after collectGarbage().
• UBSAN build (-DUBSAN=ON) on macOS:
  • Before the fix, a dedicated repro test produced a runtime error: signed integer overflow in libc++ chrono with a frame in InmemAddressRepository::calculateExpirationTime.
  • After the fix, PermanentTtlNoOverflow passes under UBSAN with no reports.
• Non‑sanitizer build:
  • ctest in build (all 67 tests passed).

Design note

An alternative would be to clamp large TTLs to max_time while still doing duration arithmetic. This change instead maps ttl::kPermanent directly to time_point::max() and leaves the existing logic for other TTLs unchanged, avoiding overflow in the sentinel case while keeping the fix minimal. A separate follow‑up issue proposes modeling permanence explicitly (e.g. a Permanent | ExpiresAt(time_point) style representation) to eliminate this class of bugs long‑term.

Screenshot

The PR includes a UBSAN screenshot taken from build-ubsan showing:

• The command:
  • UBSAN_OPTIONS=print_stacktrace=1:halt_on_error=1 ./test_bin/libp2p_inmem_address_repository_test --gtest_filter="*ReproduceKPermanentUBSAN*" (before the fix).
• The runtime error: signed integer overflow message.
• The stack frame pointing to InmemAddressRepository::calculateExpirationTime and the repro test.

Screenshot:

Closes #281