Refactor Internal Time Retrieval Handling for Improved Consistency and Resolution

[marc-mabe]

This pull request refactors how PHP internally handles current time retrieval and time measurement, introducing a more consistent and portable approach. The primary goals are to encapsulate platform-specific differences, improve time resolution, and prepare for long-term compatibility (e.g., Y2038 on WIN64).

Key Changes

• Introduced zend_time.h
  A new internal header that abstracts system time functions, replacing direct usage of <time.h> and related platform-specific APIs.

• Added zend_realtime_spec
  A unified wrapper around clock_gettime(), timespec_get(), gettimeofday(), and time() using the real/wall clock.
  Returns a timespec structure with nanosecond precision (when available).

• Defined zend_realtime_get macro
  A lightweight macro wrapping time(NULL) for simple, low-resolution time retrieval.

• Introduced zend_monotime_fallback
  A macro that maps to zend_hrtime or falls back to zend_realtime_spec.
  Useful for time measurements (e.g. timeout handling) where monotonic time is preferred, but wall time is an acceptable fallback.

• Provided helper macros
  Added utilities to simplify usage of timeval and timespec structures.

• Replaced direct system time API usage
  Internal calls to system time functions now use zend_realtime_* or zend_monotime_fallback.

• Standardized time representation
  Transitioned to timespec for current time where appropriate, while retaining timeval for files and stream-related functionality.

Benefits

• Improved Portability and Readability
  Platform-specific time logic is encapsulated, reducing conditionals and improving clarity.

• Guaranteed Time API Availability
  The new abstraction ensures time can always be retrieved via a fallback chain:
  clock_gettime() → timespec_get() → gettimeofday() → time()

• Y2038 Compatibility on WIN64
  Addresses issues caused by long in timeval.tv_sec on 64-bit Windows systems.

  Related issue: #17856 – time() and Y2038 problem on 64-bit Windows

• Improved Resolution for Time Functions
  microtime() and gettimeofday(true) now offer better time precision without breaking backward compatibility.

• Removed Redundant Availability Checks
  Previously unverified use of gettimeofday() has been replaced by a robust fallback mechanism.
  Conditional checks for microtime(), gettimeofday(), and uniqid() have been removed.