service: Reduce backend ID allocation space
service: Reduce backend ID allocation space

Currently, we store service backend ID as uint16 in the BPF maps,
which is going to be changed to uint32 in upcoming releases. Meanwhile,
the backend ID allocator allocates backend IDs as uint32 and then
casts the allocated ID to uint16.

To avoid having the same backend IDs for two different backends in
the BPF maps until the proper fix will land, make sure that the
allocator won't allocate an ID > max(uint16).

Signed-off-by: Martynas Pumputis <6b0d31c0d563223024da45691584643ac78c96e8@lambda.lt>

tgraf/cilium,cilium-team/cilium,michi-covalent/cilium,tgraf/cilium,tgraf/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,cilium-team/cilium,tgraf/cilium,tgraf/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,cilium/cilium