SqlServer Spatial: Add provider-specific functions

[bricelam]

We should consider adding (based on feedback) some of SQL Server's spatial methods to EF.Functions.

SQL Method	Notes
AsBinaryZM	Like new WKBWriter().Write(geometry)
AsGml	Like new GMLWriter().Write(geometry)
BufferWithCurves	Needs NetTopologySuite/NetTopologySuite#247
BufferWithTolerance	Like geometry.Buffer(distance, parameters)
CollectionAggregate	Needs #13278
ConvexHullAggregate	Needs #13278
CurveToLineWithTolerance	Potential workaround for NetTopologySuite/NetTopologySuite#247
EnvelopeAggregate	Needs #13278
EnvelopeAngle
EnvelopeCenter
GeomFromGml	Like new GMLReader().Read(gml)
HasM	Like double.IsNaN(point.M)
HasZ	Like double.IsNaN(point.Z)
InstanceOf	Like geometry is TGeometry
IsValidDetailed
MakeValid
MinDbCompatibilityLevel	Mitigates serialization format changes
Parse	Like new WKTReader().Read(text)
Point	Optimized version of STPointFromText
Reduce	Like simplifiers in NTS
ReorientObject
ShortestLineTo	Like DistanceOp.NearestPoints(geometry1, gometry2)
STAsText	Like new WKTWriter().Write(geometry)
STCurveN	Needs NetTopologySuite/NetTopologySuite#247
STCurveToLine	Potential workaround for NetTopologySuite/NetTopologySuite#247
STGeomCollFromText	Like new WKTReader().Read(text)
STGeomCollFromWKB	Like new WKBReader().Read(binary)
STGeomFromText	Like new WKTReader().Read(text)
STGeomFromWKB	Like new WKBReader().Read(binary)
STLineFromText	Like new WKTReader().Read(text)
STLineFromWKB	Like new WKBReader().Read(binary)
STMLineFromText	Like new WKTReader().Read(text)
STMLineFromWKB	Like new WKBReader().Read(binary)
STMPointFromText	Like new WKTReader().Read(text)
STMPointFromWKB	Like new WKBReader().Read(binary)
STMPolyFromText	Like new WKTReader().Read(text)
STMPolyFromWKB	Like new WKBReader().Read(binary)
STNumCurves
STPointFromText	Like new WKTReader().Read(text)
STPointFromWKB	Like new WKBReader().Read(binary)
STPolyFromText	Like new WKTReader().Read(text)
STPolyFromWKB	Like new WKBReader().Read(binary)
UnionAggregate	Needs #13278

[ajcvickers]

Note from triage: let's see whether it makes more sense to make a PR to NTS for the curve ones.

[ajcvickers]

Closing this as we don't intend to proactively implement these. However, this does not mean will will not implement some specific functions based on feedback, and we will likely consider well-written PRs for any of these.

[juliusfriedman]

Just as a FYI NTS Doesn't offer a comparable function for MakeValid and I am not sure if one can use the Microsoft.SqlSerer.Types package on Linux to do it manually either.