feature/conn25: clear address assignments, flow tables on profile switch

On switching from one tailnet with Connectors 2025 enabled to another,
clear the address assignments and flow tables from the previous tailnet.
They will not be useful in the new one (since the tailnet configuration
and nodes are different), and could blackhole traffic if both tailnets
happen to have a connector for the same domain.

Fixes tailscale/corp#45619.

Signed-off-by: Naman Sood <mail@nsood.in>