Werk #5688: Windows agent: numerous fixes to only_from

The setting only_from was handled improperly in many ways:

• The IPv4 loopback address 127.0.0.1 did not always work in only_from, depending on what kind of client was used on localhost. Now if the IPv4 loopback address is given in only_from, the corresponding IPv6 loopback ::1 is added there to ensure the correct functionality with different clients on localhost.
• IPv6 addresses converted from only_from IPv4 addresses were not output in section Check_MK. This was a regression from 1.2.8 introduced in the huge refactoring c5ee818358e695b01c2f2dbc05ad0713723a37f8.
• IPv6 addresses were output incorrectly in section Check_MK:
• the last colon-separated group was always missing.
• the groups were output as decimal instead of hexadecimal digits.
• the groups were output in network byte order instead of host byte order, leading to incorrect output.

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