nexthop health status don't overflow fail count

[traeak]

This is a check to ensure that failcount doesn't overflow uint32.
default ATS configuration is from https://docs.trafficserver.apache.org/en/latest/admin-guide/files/records.yaml.en.html#proxy-config-http-parent-proxy-fail-threshold

proxy.config.http.parent_proxy.fail_threshold 10

[Copilot]

Pull request overview

This pull request prevents HostRecord::failCount (a std::atomic<uint32_t>) from overflowing/wrapping when repeatedly marking a next hop down, by saturating the counter at UINT32_MAX. This aligns with ATS’s parent fail threshold behavior (default 10) while making the failure accounting robust under extreme conditions.

Changes:

• Saturate failCount increments in NextHopHealthStatus::markNextHop() to avoid uint32_t overflow.
• Fix log formatting to correctly print the uint32_t fail count using PRIu32.
• Add a unit test that forces failCount near UINT32_MAX and verifies it saturates (does not wrap to 0).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/proxy/http/remap/NextHopHealthStatus.cc	Adds saturating increment logic for failCount and updates related log format specifiers.
src/proxy/http/remap/unit-tests/test_NextHopRoundRobin.cc	Adds a regression test ensuring failCount saturates at UINT32_MAX during repeated markdowns.