Surprise! calculate-tee-times default is not the same across both DHCPv4 and DHCPv6 in Kea

Describe the bug

It can be confusing that the default setting for calculate-tee-times is false for dhcp4 and true for dhcp6 leading to configuration mistakes being made and then unexpected behaviour in production. Please annotate the ARM in both places to indicate that they're not the same (and possibly as well explain why) so that this difference doesn't trip up users who see one default and assume it's the same for both.

Alternatively, alter dhcp4 calculate-tee-times to default to true

To Reproduce

Just read the Kea ARM:

https://kea.readthedocs.io/en/latest/arm/dhcp4-srv.html#sending-t1-option-58-and-t2-option-59

https://kea.readthedocs.io/en/latest/arm/dhcp6-srv.html#controlling-the-values-sent-for-t1-and-t2-times

Expected behavior

Be not surprised ...

Environment:

All currently supported versions of Kea - the most recently released was 2.6.1

Additional Information

There's clearly some history here because Kea dhcp6 didn't used to have this option at all - it was only added in #365 (closed)

There's also some discussion in the MR about the decision to default the new option setting to true, even though the default is false for dhcp4: !296 (comment 54888)