TListOf{Functions,DataMembers}::fIds might need thread protection

[Axel-Naumann]

E.g. b1d5b97 improves the situation a bit, but in the end we're still left with many unprotected (threading-wise) accesses to both fIds and its content, i.e. addition / removal of elements might happen asynchronously. There are usages in the wild of direct access to fIds, e.g.

root/bindings/pyroot/cppyy/cppyy-backend/clingwrapper/src/clingwrapper.cxx

Lines 1902 to 1903 in 407cb58

	DataMemberInfo_t* t = gInterpreter->DataMemberInfo_Factory(did, nullptr);
	((TListOfDataMembers*)gROOT->GetListOfGlobals())->Get(t, true);

[wlav]

A priori Python code is protected by the GIL, so this access wouldn't be an issue for threaded code (GIL release is ever only on the actual call into C++, not on any setup code to reach that point). Additionally, this is a workaround for ROOT/meta's buggy handling of enums. Since that is now fixed, this particular workaround is no longer necessary and can simply be removed.

[ferdymercury]

@guitargeek I saw you were updating/syncing clingwrapper (#19906), do you think this workaround could be removed as part of your (or a separate) PR and this issue closed? Thanks