feat: redirect log

[nguyenhoangthuan99]

Fix janhq/cortex.cpp#1054
Summary changed:

• Add file_logger implementation as cortex-cpp did
• Create an interface SetFileLogger(int max_log_lines, const std::string& log_path) so that when server in cortex-cpp load engines, it can enable file logger by calling this function

[vansangpfiev]

Please move this function to the end of the class

[nguyenhoangthuan99]

I'll remove it

[dan-menlo]

Question: is this settable via .cortexrc? (and is it per-engine specific?)

[nguyenhoangthuan99]

New logger don't need that config, I'll remove max_log_file_size

[dan-menlo]

@nguyenhoangthuan99 I've approved this PR to unblock you.

However, can I verify my understanding of this PR, and the separation of concerns between the main cortex and llama.cpp-engine

• cortex.llamacpp has its own file logger (?)
• cortex.cpp uses SetFileLogger to pass the path to the llama.cpp engine, which then implements its own file logging

I have the following questions:

• If we run multiple engines, will there be lock problems on the log file (or is it one process with cortex.cpp?)
• If each engine implements its own logging, will there be a standardized logging format? (e.g. from Trantor verbose, with timestamps)

[nguyenhoangthuan99]

@nguyenhoangthuan99 I've approved this PR to unblock you.

However, can I verify my understanding of this PR, and the separation of concerns between the main cortex and llama.cpp-engine

• cortex.llamacpp has its own file logger (?)
• cortex.cpp uses SetFileLogger to pass the path to the llama.cpp engine, which then implements its own file logging

I have the following questions:

• If we run multiple engines, will there be lock problems on the log file (or is it one process with cortex.cpp?)
• If each engine implements its own logging, will there be a standardized logging format? (e.g. from Trantor verbose, with timestamps)

• When we run multiple engines, all engines still run in the same process, but they can in different thread, so the lock problem won't appear.
• The File logger implementation is copied from cortex.cpp so every format still the same, this is a limitation happened when we separate into many repos, some part of code cannot be reused and we have to copy it manually