Improve performance: CharBufferToWritableSequentialData.read/writeBytes

The `CharBufferToWritableSequentialData` implements the `WritableSequentialData` and `ReadableSequentialData` interfaces. However, it delegates bulk operations to the default implementations in these interfaces which are slow because they run explicit loops calling read/writeByte (note the singular) methods for each individual byte.

All these operations can be potentially optimized if the read/writeBytes (note the plural) methods are overridden in `CharBufferToWritableSequentialData` to use bulk data transfers (like Arrays.copy and similar.)

For more details, see https://github.com/hashgraph/pbj/issues/191