Add a new .spec.tailscale.acceptRoutes field to ProxyClass,
that can be optionally set to true for the proxies to
accept routes advertized by other nodes on tailnet (equivalent of
setting --accept-routes to true).
Updates tailscale/tailscale#12322,tailscale/tailscale#10684
Signed-off-by: Irbe Krumina <irbe@tailscale.com>