Fix compute_follow_kernel_items to properly index bool array per kernel

[ydah]

Fix a bug where each kernel was mapped to the full Bitmap.to_bool_array result (Array[bool]) instead of its indexed bool value.
Since arrays are always truthy in Ruby, follow_kernel_items[goto][kernel] evaluated to true for every kernel, making the filtering in goto_follow_set (Definition 3.39) and lhs_contributions (Definition 3.31) ineffective.

The fix computes the bool array once and assigns each kernel its corresponding value:

# Before (buggy): every kernel mapped to the full bool array
state.follow_kernel_items[goto] = state.kernels.map {|kernel|
  [kernel, Bitmap.to_bool_array(follow_kernel_items, state.kernels.count)]
}.to_h

# After: each kernel mapped to its corresponding bool value
bool_array = Bitmap.to_bool_array(follow_kernel_items, state.kernels.count)
state.follow_kernel_items[goto] = state.kernels.each_with_index.to_h {|kernel, i|
  [kernel, bool_array[i]]
}