setup: rename `check_repository_format_gently()`

setup: rename `check_repository_format_gently()`

The function `check_repository_format_gently()` receives a format as
input. An unknowing reader may thus suspect that this function actually
checks the passed-in format for consistency. While the function indeed
checks the repository format, it actually serves two purposes:

  - It reads the repository's format and populates the passed-in format
    with that information.

  - It then indeed checks whether the format is consistent.

Rename the function to `read_and_verify_repository_format()` to clarify
its functionality. While at it, reorder the parameters so that the
format comes first to better match other functions that pass around the
format.

Signed-off-by: Patrick Steinhardt <redacted>
Signed-off-by: Junio C Hamano <redacted>