Proper guarding of service instances in CSIP module

[niym-ot]

There needs much better or larger changes in the CSIP module to properly guard the service instance modifications.

Also test cases needs to be added for the same

Also below point needs to be considered
"if CONFIG_BT_BONDABLE=n, then there's some parts of our code that shouldn't be run (should be guarded by CONFIG_BT_BONDABLE), but I think we can do that in a follow-up PR, but something like this probably should since it's only dealing with bonds at the moment"

Reference - #88402

[Thalley]

@niym-ot Please follow the templates when creating a Github issue