[PROJ] Tie breakers used when ordering candidate operations

[Even Rouault]

Hi Nyall,

Obviously the doc was lagging a bit behind the latest state of the code. 
Update in https://github.com/OSGeo/PROJ/pull/2522

> 11. consider as more relevant an operation that involves less
> transformation steps
> 
> Here I'd have thought 8450 (with a single noop step) would be picked
> over 9690, which has a pipeline of:
> 
> +proj=pipeline
>   +step +proj=axisswap +order=2,1
>   +step +proj=unitconvert +xy_in=deg +xy_out=rad
>   +step +proj=push +v_3
>   +step +proj=cart +ellps=WGS84
>   +step +proj=helmert +x=0.06155 +y=-0.01087 +z=-0.04019 +rx=-0.0394924
>         +ry=-0.0327221 +rz=-0.0328979 +s=-0.009994
> +convention=coordinate_frame +step +inv +proj=cart +ellps=GRS80
>   +step +proj=pop +v_3
>   +step +proj=unitconvert +xy_in=rad +xy_out=deg
>   +step +proj=axisswap +order=2,1

If you look at the WKT output, you'll see that both have a single 
transformation step, which is what is considered by the sorting algorithm. But 
a helmert transformation with no translation and no rotation can be simplified 
in a single PROJ operation.

So here only the final criterion apply. Given that "WGS 84 to GDA2020 (3)" > 
"Inverse of GDA2020 to WGS 84 (2)" in lexicographic order, it has higher 
precedence. Completely arbitrary here obviously...

Even

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