feat(NODE-5919): support new type option in create search index helpers

[baileympearson]

Description

What is changing?

Add support for the type field in SearchIndexDescription. Also syncs the unified search index tests and adds two new search index prose tests, as added in https://jira.mongodb.org/browse/DRIVERS-2768.

Is there new documentation needed for these changes?

What is the motivation for this change?

Release Highlight

type supported in SearchIndexDescription

It is now possible to specify the type of a search index when creating a search index:

const indexName = await collection.createSearchIndex({
  name: 'my-vector-search-index',
  // new! specifies that a `vectorSearch` index is created
  type: 'vectorSearch',
  definition: {
    mappings: { dynamic: false }
  }
});

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