Fix IPv4 byte order handling

[FranciscoMaxwell]

Fixes #521.

Summary

This fixes inconsistent byte-order handling in ColumnIPv4:

• Append(std::string) now stores the network-order value returned by inet_pton without applying a second byte swap.
• Append(in_addr) now stores in_addr::s_addr as-is, matching the platform/network-order representation used by socket APIs.
• At() and operator[] now return the stored network-order representation directly.
• Append(uint32_t) and the vector constructor continue to accept host-order integer values.
• Adds coverage proving string, host-order integer, and in_addr appends serialize to the same bytes.

Testing

• cmake -S . -B build -DBUILD_TESTS=ON
• cmake --build build --target clickhouse-cpp-ut --config Debug --parallel 4
• .\build\ut\Debug\clickhouse-cpp-ut.exe --gtest_filter="ColumnsCase.ColumnIPv4*"
• git diff --check

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