fix(NODE-6536): Binary.read never returns number[] and reads beyond content

[nbbeeken]

Description

What is changing?

• Fix Binary.read return type to be correctly Uint8Array
• Use subarray instead of slice so there isn't inconsistent view/copy between node and web
• Prevent reading beyond serializable user data
• Remove dead code from deserializer (buffer.slice is always defined)
• Searched for our usages of slice when we mean to use subarray to get views not copies. This has no impact on Node, fixes browser environments making copies where we did not intend to

Is there new documentation needed for these changes?

No

What is the motivation for this change?

Correctness and consistency

Release Highlight

Binary's read() returns a view of Uint8Array

Binary's read() return type claimed it would return number[] or Uint8Array which was true in previous BSON versions that didn't always store a Uint8Array on the buffer property like Binary does today.

read()'s length parameter did not respect the position value allowing reading bytes beyond the data that is actually stored in the Binary. This has been corrected.

Additionally this method returned a view in Node.js environemnets and a copy in Web environments. it has been fixed to always return a view.

Double check the following

• Ran npm run check:lint script
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket