Use `maxele.gr3` for maximum elevation results

[SorooshMani-NOAA]

Currently the out_2d*.nc file is used to get the max-elevation dataset for analysis:

EnsemblePerturbation/ensembleperturbation/parsing/schism.py

Lines 719 to 726 in 1fbaf14

	class MaximumElevationOutput(MaximumScalarFieldOutputCalculator):
	"""
	``out2d.nc`` - Derived Maximum Elevation at All Nodes in the Model Grid
	"""
	out_filename = 'schism_max_elevation.nc'
	file_patterns = ['out2d_*.nc']

I think the main reason behind that is the missing maximum elevation time in the gr3 file. Since the timing data is not currently being used, maybe it makes more sense to just use the maxelev.gr3 values instead. out2d_* is output is controlled by output step, while maxelev.gr3 is the actual maximum.

Just FYI @FariborzDaneshvar-NOAA

[FariborzDaneshvar-NOAA]

@SorooshMani-NOAA thanks for looking into this. Based on my experience working with outliers of with/out NWM, elevations from maxelev.gr3 could be much higher than out2d_*.nc, and the reason is that the first one includes the entire time period and might include noises from the earlier times! Here is one example: https://github.com/noaa-ocs-modeling/SurgeTeamCoordination/issues/115#issuecomment-1740210537