HLTReprocessing prescale set follow ups

MenuPrescaleConfig.py - Prescale values shouldn't be stored as strings in the JSON file (spotted by @kkapusci)

before	after
"prescale": "-1",	"prescale": -1,
"prescale": "10",	"prescale": 10,

Changing test_trigP1_v1Dev_dumpConfig_build.py and test_trigP1_v1Dev_noL1Sim_dumpConfig_build.py to both use the menu Dev_pp_run3_v1_HLTReprocessing_prescale otherwise we have no tests that create the correct JSON files in ART to then be uploaded for a HLT reprocessing (cc @ballbroo, @tnobe, @astruebi, @palacino). This makes these tests different to other Dev menu tests so notifying @khoo @sshaw @vmartin @martindl, but as these tests only dump JSON files I believe the inconsistency is ok.