XCAFDoc_LayerTool extended to work with layer defined by its label

RLN contribution (RLN_fix440)
- Summary: XCAFDoc_LayerTool extended to work with layer defined by its label,
not string
- Detailed description: Added methods IsSet(), UnSetOneLayer(), GetLayers() that
accept TDF_Label or TDF_LabelSequence in addition to TCollection_ExtendedString
or TColStd_HSequenceOfExtendedString.
These methods allow for better performance as avoid searching for the layer
label using its string.

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Branch OCC22594_XcafdocDoctoolDestructor is created.