Remove IVertexFitter base class and introduce vertex fitter concept

Closes #617 (closed)

changed milestone to %0.12.00

added Improvement label

added 61 commits

• 535c0202...7d05279c - 57 commits from branch master
• d55443ce - replace IVertexFitter interface by templated vfitter
• 8ac1d2f9 - fix format after rebase
• 3733bc71 - add vertex fitter concept
• dfa9e3c3 - add vertex fitter concept

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unmarked as a Work In Progress

changed title from WIP: Remove IVertexFitter base class and introduce concepts to Remove IVertexFitter base class and introduce vertex fitter concept

changed the description

@pagessin or @rlangenb, can you review? :)

approved this merge request

resolved all discussions

merged

mentioned in commit 81c1adc1

changed milestone to %0.10.03

mentioned in merge request atlas/atlasexternals!547 (merged)

mentioned in merge request atlas/athena!26660 (merged)