Switch ITk vertexing to AMVF with more optimal settings
For studies of the ITk in release 20.20, the Adaptive Multi Vertex Fitter was found to perform much better than the Iterative finder. This MR switches the default ITk vertexing to use AMVF, and also updates the default AMVF settings according to those found to give better CPU performance in ATLIDTRKCP-245. Other CPU optimizations made to address the large CPU time increase observed in release 22 when switching to this as the default should be considered for back-porting.
(Careful checks in e.g. SPOT should anyway be made once this is merged)
This causes changes in the vertexing output as would be expected (most noticeably it results in ~1.7 vertices rather than 1 per event in standard tests on a ttbar signal sample).
Edited by Nicholas Styles