Bluetooth: Host: `_bt_gatt_ccc.value` may include disconnected peers

[alwa-nordic]

When CONFIG_BT_SETTINGS_CCC_LAZY_LOADING=n, the value of _bt_gatt_ccc.value is affected by CCC values from all bonds, not just connected peers.

The documentation for _bt_gatt_ccc.value specifies that only connected peers contribute to that value.

zephyr/include/zephyr/bluetooth/gatt.h

Lines 939 to 940 in 6798064

	/** Highest value of all connected peer's subscriptions */
	uint16_t value;

This bug makes the behavior of _bt_gatt_ccc.value depend on the state of CONFIG_BT_SETTINGS_CCC_LAZY_LOADING, so it cannot reasonably be fixed by keeping behavior and updating documentation.

See also discussion #79822