SDKv3-09: Update naming and documentation for `@aws-cdk/sdk-v2-to-v3-adapter`

[TheRealAmazonKendra]

Context

The AWS SDK V2 is being deprecated. We need to remove all uses of it from the CDK.

Task Description

We need to update the name so that it doesn't imply that v2 is still usable. Documentation updates are also needed. No code changes at this time.

Acceptance Criteria

• The name has been changed
• The documentation makes it more clear what the tooling does and how it works

[github-actions]

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[aws-cdk-automation]

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