Use + std::to_string to convert integers before appending to a string

[jmcarcell]

BEGINRELEASENOTES

• muonSystemMuRWELL_o1_v01.cpp: Use + std::to_string to append to a string, instead of adding an integer to a string (introduced in [IDEA] Adding the detailed version of the muon system. #322). Adding a string and an integer cuts the string by as many characters as the value of the integer.

ENDRELEASENOTES

See https://gcc.godbolt.org/z/qfojcnMK9 for an example. Should we worry that this has not been caught when testing? @mahmoudali2 @BrieucF

[BrieucF]

Thanks for spotting this Juan! I guess it would be difficult for the tests to see this, there is nothing wrong per-se and the names were still "unique" since the number of character being cut were different.

[jmcarcell]

I'm merging this since it has been up for 1 month, feel free to edit in another PR