TMinuit and TH2::DoProjection interfere when using threads

CMS has been seeing a periodic crash involving TH2::DoProjection while another thread happens to be doing a minimization. The incidents can be seen here
https://github.com/cms-sw/cmssw/issues/18620

The problem is the following:
TH2::DoProjection calls TROOT::FindObject
https://root.cern.ch/doc/master/TH2_8cxx_source.html#l02086

TROOT::FindObject reads fSpecials without taking the lock
https://root.cern.ch/doc/master/TROOT_8cxx_source.html#l01202

while TMinuit manipulates the list of specials while holding a lock. E.g.
https://root.cern.ch/doc/master/TMinuit_8cxx_source.html#l00463

If TH2::DoProjection is running concurrently as TMinuit is begin used, it leads to a data race which causes the crash.