Revert incorrect hydrolib-core expected values

[veenstrajelmer]

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Description

In #139 some mdu keywords were updated to new values.

Were empty before:

dzTop                      = -999                                                           # Z-layer thickness of layers above level Dztopuniabovez
floorLevTopLay             = -999                                                           # Floor level of top layer
dzTopUniAboveZ             = -999                                                           # Above this level layers will have uniform dzTop, below we use sigmaGrowthFactor
bgrwuni                  = -999     # uniform level of impervious layer, only used if h_aquiferuni is negative.
sgrwini                  = -999 # Initial groundwater level, if h_unsatini < 0.
trtDef = .    # File (*.ttd) including trachytope definitions.
trtL   = .    # File (*.arl) including distribution of trachytope definitions.
outputDir                         = .      # Output directory of map-, his-, rst-, dat- and timingsfiles, default: DFM_OUTPUT_<modelname>. Set to . for no dir/current dir.
waqOutputDir                      = .      # Output directory of Water Quality files.

Not existent before:

fixedWeirTopFrictCoef = -999 # Uniform friction coefficient of the groyne part of fixed weirs [the unit depends on frictiontype].

Especially the . values are not expected, these might cause issues and they might not. This has been reported in hydrolib-core.

Todo:

• wait for Empty path gets upgraded to pathlib.Path(".") by FMModel HYDROLIB-core#703 fix (and new release)
• update minimal hydrolib-core version
• revert values in examples/dflowfm_local/dflowfm/DFlowFM.mdu
• revert values in examples/dflowfm_piave/dflowfm/DFlowFM.mdu
• update test_read_write_config_empty_paths