Make new directory under federated named network

[Jakio815]

This PR is the first step abstracting the network layer which is in #281.

This changes the file structure of the reactor-c, adding a new directory under federated named networks.

Currently only moved net_util.c net_common.h and net_util.h under newly named directory networks.

This is to add more files in future such as net_tls.c.

The corresponding CMakelists.txt files have been modified together.

The idea comes from how the platform works. Each platform related header such as lf_arduino_support.h lf_rp2040_support.h is inside the directory platform.

This must be merged together with lf-lang/lingua-franca#2070

[Jakio815]

@lhstrh This was discussed in the security meeting. The point is just moving network related c and header files under a directory network. Do you think it's fine?

[lhstrh]

I would call network or net, not networks, but the idea seems fine. Let me request review from @erlingrj.

[erlingrj]

Looks like a reasonable approach. Just one question about the new CMakeLists.txt

[Jakio815]

I would call network or net, not networks, but the idea seems fine. Let me request review from @erlingrj.

Fixed all to network

[Jakio815]

@lhstrh Can I merge this together with lf-lang/lingua-franca#2070?

[lhstrh]

I noticed that not all test in lf-lang/lingua-franca#2070 are passing though...

[lhstrh]

Looks good modulo comment.

[Jakio815]

@lhstrh Oops. Sorry for that. I thought it was finished. The lingua-franca's check is finished now, but I see that the reactor-c is being kept updated by Professor Lee. Should I merge it after his update is finished?

[lhstrh]

I think it's OK to just go ahead and merge once the tests pass.

[edwardalee]

As long as you are using reactor-c/main it is OK to merge this.