fix(NODE-6827): incorrect negative bigint handling

[W-A-James]

Description

What is changing?

Is there new documentation needed for these changes?

What is the motivation for this change?

Release Highlight

⚠️ Fixed potential data corruption bug when useBigInt64 is enabled

After refactoring to improve deserialization performance in #649, we inadvertently introduced a bug that manifested when deserializing Long values with the useBigInt64 flag enabled. The bug would lead to negative Long values being deserialized as unsigned integers. This issue has been resolved here.

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

[baileympearson]

patch: https://spruce.mongodb.com/version/67c9d46a35027a0007e51a2b/tasks?sorts=STATUS%3AASC%3BBASE_STATUS%3ADESC

TS failures unrelated. Node latest tests are failing because bf5b66e is missing, and the Node18 tests are failing because we need to specify a minimum npm version. But node 16 and 20 pass.