pfSense

Handle empty values during config upgrade. Fix #15362

The config may have an empty string - use 'empty()' instead of
'isset()' since '0' is not valid in this case.

Update the interface cache when configuring IPsec. Fix #15449

Introduce a default return value to the rest of the config functions

The current return values remain the same. The added safety checks
ensures the correct type when calling array_* functions, and allows
for more flexible error handling.

Clean up rule generation code for state-tracking options

Improve readability and make it easier to adjust for future changes.

Automatically use floating states for IPsec rules. Fix #15430

Avoid configuration loop with LAGG interfaces. Fix #14083

The fix to #9453 introduced a loop when configuring LAGG interfaces.
This happens when interface_lagg_configure() ultimately calls
set_interface_mtu() which also calls interface_lagg_configure(). Since...

Default to an empty array for functions expecting a countable value

Do this for foreach() and count().

Correct default for 'system/acb' in write_config() to empty array instead of null

Update all direct config access with accessor functions

Refactor config upgrade to use config accessors