net: compat.h related cleanup

Summary:

net: Drop unneeded Windows headers in compat.h

No interface from the mswsock.h header is used.
According to https://docs.microsoft.com/en-us/windows/win32/winsock/creating-a-basic-winsock-application
"The Winsock2.h header file internally includes core elements from
the Windows.h header file, so there is not usually an #include line
for the Windows.h header file in Winsock applications."

net: Drop unneeded headers when compat.h included

net: Add compat.h header for htonl function

This is a backport of core#20221

Test Plan:
ninja all check-all

Run windows builds on CI.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10993