env: move "sparse_expect_files_outside_of_patterns" into `repo_config_values`

env: move "sparse_expect_files_outside_of_patterns" into `repo_config_values`

The `core.sparseCheckoutExpectFilesOutsideOfPatterns` configuration was
previously stored in a global `int` variable, making it shared across
repository instances and risking cross‑repository state leakage.

Store it instead in `repo_config_values`, where eagerly‑parsed
repository configuration lives. This option is parsed eagerly because
it controls how sparse‑checkout paths are interpreted – a fundamental
behavior that many commands rely on; a lazy parse could cause
inconsistent sparse‑checkout handling and complicate libification.
This preserves the existing 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>
Mentored-by: Usman Akinyemi <usmanakinyemi202@gmail.com>
Signed-off-by: Olamide Caleb Bello <belkid98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>