Centralize interposer init with pthread_once and use CLOCK_MONOTONIC

[Religious-J]

Motivation

• Harden and centralize initialization of the malloc interposer to avoid racey per-function lazy init and ensure consistent real-function resolution.
• Improve timestamp stability and avoid allocator reentrancy issues while recording backtraces and ensure symbol buffers are freed to prevent leaks.

Description

• Replace per-wrapper lazy initialization with a single init_real_functions invoked via pthread_once, and store resolved pointers in malloc_cp, realloc_cp, calloc_cp, and free_cp.
• Replace gettimeofday with monotonic timing using clock_gettime(CLOCK_MONOTONIC) in get_cur_ms and initialize time_base during init.
• Make the recording guard allow_record thread_local and mark globals as static to limit scope, then call pthread_once at the start of each wrapper (malloc, realloc, calloc, free).
• Free the buffer returned by backtrace_symbols with free_cp(symbols) after logging to avoid leaking that memory.

Testing

• No automated tests were run for this change.

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Codex Task