Deprecate torch::nn::modules_ordered_dict API

[yf225]

I finally found a way to get the following API to work for constructing a list of named submodules for Sequential:

Sequential sequential({
  {"m1", MyModule(1)},
  {"m2", MyModule(2)}
})`

which was actually our original proposed design and much simpler than our current API:

Sequential sequential(modules_ordered_dict({
  {"m1", MyModule(1)},
  {"m2", MyModule(2)}
}));

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[facebook-github-bot]

@yf225 merged this pull request in 5804e54.