feat(NODE-6031): add t and i to Timestamp

[nbbeeken]

Description

What is changing?

• add t and i getters to Timestamp
• change internals to use getters

Is there new documentation needed for these changes?

No

What is the motivation for this change?

• users do not have to recall whether t or i is the high or low bits
• a Timestamp can be constructed from another Timestamp

Release Highlight

Timestamp now has t and i properties

To make this type a bit easier to use we are surfacing the breakdown of the two internal 32 bit segments of a Timestamp value.

const ts = new Timestamp({ i: 2, t: 1 });
ts.i // 2
ts.t // 1

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

[aditi-khare-mongoDB]

Small testing naming change, thanks for finishing this up so quick!