Improve logging logic

[Gurjaka]

We had cases where we wanted to debug code using the pretty_log system. Our logging levels are defined as:

enum log_level {
    PRETTY_ERROR,
    PRETTY_WARN,
    PRETTY_INFO,
    PRETTY_DEBUG
};

The main issue was that PRETTY_DEBUG logs were still emitted in RELEASE builds.

Note: Logging can be expensive, and unnecessary debug statements can significantly impact the emulator’s performance.

This PR introduces two commits:

1. Compile-time debug filtering:
   Using the C preprocessor, PRETTY_DEBUG logs are only included when the binary is built with DEBUG_MODE. This ensures debug logs are removed from release builds entirely.

2. Time caching optimization:
   pretty_log_get_time() now caches the last retrieved time (time_t last) and only updates when the current time (time_t now) changes. This eliminates redundant syscalls, reducing overhead in frequent logging scenarios.