Fix definition of "listen" of net$Server and its subclasses

[Rob--W]

The listen signature of net$Server did not match the definition of
the actual API at https://nodejs.org/api/net.html#net_server_listen

In particular, flow failed to detect invalid handles and options due to
the use of an object with all-optional properties, and the use of
Function (which is an alias for any).

This patch fixes the following issues:

• Remove repeated method declarations of net$Server from its subclasses, and add missing listen methods to net$Server.
• Callbacks are no longer typed Function (which is equivalent to any), but () => mixed.
• Rename the listen's handle parameter to options.
• Require the options object to either contain path or port.
• The listen method with parameter handle has a type definition.

Fixed the following issues with node_tests:

• All existing node_tests that were marked with "These should fail" are now failing as expected.
• handle renamed to options.
• fd renamed to path (string values are path, not fd).
• Add new passing tests for listen(handle, ...).
• Treat empty objects as a failure (because port or path is required).

The number of expected node_tests failures increased from 115 to 131.
12 of those are tests that were marked as "failing" but did not.
The other 4 are signatures that were marked as "passing" but should have
failed (fd with string value instead of number, and empty object).