environment: move "trust_ctime" into `struct repo_config_values`
The `core.trustctime` configuration is currently stored in the global variable `trust_ctime`, which makes it shared across repository instances in a single process. Store it instead in `repo_config_values`, where eagerly‑parsed repository configuration lives. `core.trustctime` is parsed eagerly because it is used in low‑level stat‑matching functions (`match_stat_data()`), where a lazy parse could cause unexpected fatal errors, result in a performance regression and complicate libification efforts. This preserves that behavior while tying the value to the repository from which it was read, avoiding cross‑repository state leakage and continuing the effort to reduce reliance on global configuration state. Update all references to use repo_config_values(). Mentored-by: Christian Couder <christian.couder@gmail.com> Signed-off-by: Olamide Caleb Bello <belkid98@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>