Remove obsolete DEBUG only instance variable BasicBlock::bbLoopNum (#34652)

Remove obsolete DEBUG only instance variable BasicBlock::bbLoopNum (#34652)

* Remove obsolete DEBUG only instance variable BasicBlock::bbLoopNum

Comment at declaration in block.h

    // This is the label a loop gets as part of the second, reachability-based
    // loop discovery mechanism.  This is apparently only used for debugging.
    // We hope we'll eventually just have one loop-discovery mechanism, and this will go away.
    INDEBUG(loopNumber bbLoopNum;) // set to 'n' for a loop #n header

* Run jit-format