kernel: modules: split package fs-fscache

kernel: modules: split package fs-fscache

The module kmod-fs-fscache was merged into kmod-fs-netfs since
6.12 LTS kernel[1]. Therefore, we have to split fs-cachefiles
into a separate package. This patch also removed some outdated
config symbols that have already been removed in 5.15 kernel:

CONFIG_FSCACHE_OBJECT_LIST [2]
CONFIG_{FSCACHE,CACHEFILES}_HISTOGRAM [3]

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.12.y&id=915cd30cdea8811cddd8f59e57dd9dd0a814b76c
[2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.15.y&id=58f386a73f16cea1f78e8466cc5c402eb7f6fcf8
[3] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.15.y&id=6ae9bd8bb037b7c422bafde746f2338a716f6058
Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/18661
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>