Add missing fstream includes triggered by using boost 1.86
In Gaudi 38r3 there are a few missing #include <fstream> - the compilation errors are triggered by using boost 1.86 as discussed in SPI-2635
In Gaudi 38r3 there are a few missing #include <fstream> - the compilation errors are triggered by using boost 1.86 as discussed in SPI-2635