…s and 200 MiB/s

### Work
Implement new BlobReadChannelV2 which replaces BlobReadChannel and improves on
its resource usage to reduce min number of RPCs to 1 from (objSize / chunkSize + 1)
while still maintaining the ability to restart a stream that may have been
interrupted.

### Results
Throughput in MiB/s has increased across the board:
```
        ClassName           mean    25%    50%    75%    90%    95%    99%    max
READ[0] BlobReadChannel     32.2   25.3   29.0   32.6   42.1   56.1  111.9  214.1
READ[1] BlobReadChannel     32.1   25.4   28.7   32.6   41.7   55.4  106.1  224.4
READ[2] BlobReadChannel     31.9   25.2   28.6   32.8   41.6   55.2  105.4  227.2
READ[0] BlobReadChannelV2  214.1  196.4  219.8  239.3  254.3  261.2  278.0  315.2
READ[1] BlobReadChannelV2  215.9  198.8  221.0  240.0  254.4  261.8  281.8  315.6
READ[2] BlobReadChannelV2  216.4  199.5  221.2  239.4  253.9  261.6  281.6  308.6
```

Data collected using all default settings, against a regional bucket,
across a range of object sizes [256KiB, 2GiB]. Each object is read in full three
times to account for any GCS caching variability.

### Internal implementation notes
Add ByteRangeSpec to encapsulate relative vs explicit(open) vs explicit(closed)
vs null vs open-ended ranges and their associated logical subtleties.

New StorageReadChannel interface possible candidate for new storage specific
interface we can expose to folks for improvements independent of core and
BigQuery.

ClientStuff is no longer Serializable. Instead, BlobReadChannelV2State will store the instance of HttpStorageOptions and then reconstitute the BlobReadChannelContext at restore() time.

In order to facilitate migrating any RestorableState<ReadChannel> customers might have, we leave the existing class hierarchy in place and update BlobReadChannel.StateImpl#restore() to produce a new BlobReadChannelV2.

In the next major version this compatibility path will be removed.

To test compatibility a serialized instance of a BlobReadChannel from v2.16.0 has been created and serialized into blobWriteChannel.ser.properties along with a comment describing how the ser was generated.