[C++] Add iterator-based variants of bit-run visitors

### Describe the enhancement requested

`VisitBitRuns`, `VisitSetBitRuns`, `VisitTwoSetBitRuns` are useful in many cases but some times the caller needs to control the control flow, for example for returning early.

So it would be nice to be able to write:
```c++
for (const auto run : IterateBitRuns(bitmap, offset, length)) {
// do something with run.position, run.length, run.set
}
// or:
for (const auto run : IterateSetBitRuns(bitmap, offset, length)) {
// do something with run.position, run.length
}
// or:
for (const auto run : IterateTwoSetBitRuns(
left_bitmap, left_offset, right_bitmap, right_offset, length)) {
// do something with run.position, run.length
}
```

The same transformation could be done for `VisitBitBlocks`, `VisitTwoBitBlocks`.

### Component(s)

C++

Start by reading the existing VisitBitRuns, VisitSetBitRuns, VisitTwoSetBitRuns, VisitBitBlocks, and VisitTwoBitBlocks entry points and their current C++ tests. Confirm the iterator variants support the shown range arguments and early-exit use case, with tests covering the run or block values and behavior for each variant.

Written by the indexing model from the issue text.