Add infinite reconnect_timeout and configurable reconnect_interval

Added capabilities for managing reconnect_timeout and reconnect_interval:

--reconnect_timeout can be set to -1 for infinite reconnection attempts. This is necessary for ensuring the durability of connections for remote unmanaged hosts in the VPN.

--reconnect_interval has been added as a new parameter and can be set to a fixed value for quicker reconnections. The current maximum value of 100 seconds may be too long. If the --reconnect_interval option is missing in the CLI, the progressive interval (as it works now) will be used. A new boolean option has been added to the API void openconnect_set_progressive_reconnect_interval(struct openconnect_info *vpninfo, unsigned val) to implement this feature. The default value is true to maintain the previous behavior.

Thus, the added capabilities will not change the default behavior and will not affect users who do not need them.

Please review the TODO strings in openconnect.h to correctly determine the proper API and application versions.

Also I add MR to GUI version openconnect-gui!320

! I cannot run the pipelines because I am unable to verify my account due to my telephone number not being accepted.