use std::vector in blocks that take JSON vectors

[guruofquality]

• std::vector would make more sense in these cases, its the native "list of numbers" format.
  • also same issue in opencl kernel block constructor
• require: pothosware/pothos-util#1
• require: pothosware/pothos-util#4

[guruofquality]

pothosware/PothosCore@44f7faf