feat(time_checks): add timechecks

[Ayoubnac1]

Currently working on " time checks "
│ │ ├── time_checks # Dedicated file for time-related checks
│ │ │ ├── check_time_monotonicity.py # Checks if the time variable is monotonic
│ │ │ ├── check_time_uniqueness.py # Checks if the time values are unique
│ │ │ ├── check_time_bounds.py # Checks if the time variable has valid bounds
│ │ │ ├── check_time_gaps.py # Checks for gaps in the time series
│ │ │ ├── check_time_units.py # Checks the units of the time variable
│ │ │ ├── check_time_calendar.py # Checks the calendar attribute of the time variable