Allow overriding MAX_RTR_SOLICITATIONS via configuration option

[tsndqst]

Can a configuration option be created to set MAX_RTR_SOLICITATIONS at runtime?

I have a problem with my laptops that use Intel WiFi drivers. There is a known problem with Intel firmware that prevents the WiFi driver from receiving the RAs sent by the router. My current workaround for this is to run sudo rdisc6 -r 30 wlo1 once dhcpcd has given up.

I recently changed MAX_RTR_SOLICITATIONS to 30 and was able to receive an RA without resorting to running rdisc6. Having to patch dhcpcd every time a new version comes out would get tiresome.

The Intel firmware issue is a problem on Windows and Linux. Several forum posts describe the issue:
https://community.intel.com/t5/Wireless/Connectivity-Issue-IPv6-on-Wireless/td-p/647199
https://community.intel.com/t5/Wireless/AX201-Stateless-Autoconfiguration-IPv6-not-working-reliably/m-p/1364020#M40716
https://community.intel.com/t5/Wireless/Can-t-takel-always-IPv6-when-connect-to-a-router/m-p/1351913