v4.2.0

• Fixed the compile-time exclusion of log levels. Renamed the QUILL_COMPILE_OUT_LOG_LEVEL preprocessor
  flag to QUILL_COMPILE_ACTIVE_LOG_LEVEL.
• Fixed build error when UnboundedDropping queue is used.
• Fixed a bug introduced in v4.1.0, which resulted in messages being logged out of order when
  the transit_events_soft_limit was reached. Additionally, this issue affected the behavior of flush_log(),
  prematurely unblocking the thread before all messages were flushed.
• Fixed -Wno-unused-parameter and -Wdocumentation warnings.
• Improved backend worker _exit() functionality and reduced code duplication in other areas of the backend worker code.
• Added signal_handler_timeout_seconds parameter, which controls the timeout duration for the signal handler. Only
  available on Linux platforms.
• Added sleep_duration_ns parameter to the flush_log(...) function. This parameter specifies the duration in
  nanoseconds to sleep between retries between checks for the flush completion and when a blocking queue is used,
  and it is full. The default sleep duration is 100 nanoseconds, but users can now customize this duration according to
  their needs. If a zero sleep duration is passed, the thread might yield instead.
• Removed uses of std::this_thread::sleep_for(...), std::string, std::vector in the signal handler when waiting for the log to be flushed.