feat(read-stream): Refactor & optimize BlockMap.ReadStream

[jhermsmeier]

This is a major refactoring & optimization of the blockmapped ReadStream to iron out some performance issues and bugs in behavior.

Changes:

• Add debug module
• BREAKING: Remove .blockInRange property
• Add .closed & .destroyed properties
• Convert blockMap's ranges to byte ranges for simplified block reading
• Add .highWaterMark getter/setter
• Support autoClose option
• Rewrite ._readBlock() to read up to highWaterMark chunks within a range to increase throughput, and decrease CPU load and read calls
• BREAKING: Rewrite open(), close() and destroy() to implement the same behavior as fs.ReadStream
• BREAKING: start & end options will now cause only partially covered regions to NOT be read
• BREAKING: Remove .options, add .verify instead
• Update tests to match above changes

Change-Type: major