unbundle: extend object verification for fetches

unbundle: extend object verification for fetches

The existing fetch.fsckObjects and transfer.fsckObjects configurations
were not fully applied to bundle-involved fetches, including direct
bundle fetches and bundle-uri enabled fetches. Furthermore, there was no
object verification support for unbundle.

This commit extends object verification support in `bundle.c:unbundle`
by adding the `VERIFY_BUNDLE_FSCK` option to `verify_bundle_flags`. When
this option is enabled, we append the `--fsck-objects` flag to
`git-index-pack`.

The `VERIFY_BUNDLE_FSCK` option is now used by bundle-involved fetches,
where we use `fetch-pack.c:fetch_pack_fsck_objects` to determine whether
to enable this option for `bundle.c:unbundle`, specifically in:

- `transport.c:fetch_refs_from_bundle` for direct bundle fetches.
- `bundle-uri.c:unbundle_from_file` for bundle-uri enabled fetches.

This addition ensures a consistent logic for object verification during
fetches. Tests have been added to confirm functionality in the scenarios
mentioned above.

Reviewed-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Xing Xin <xingxin.xx@bytedance.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>