Add MemoryClient for AgentCore Memory

## Description

The TypeScript SDK currently has no support for AgentCore Memory. Customers need a client that provides a convenient interface over the Memory control plane and data plane APIs, similar to what exists in the [Python SDK](https://github.com/aws/bedrock-agentcore-sdk-python).

## Motivation

Today, customers must use the raw AWS SDK clients (`@aws-sdk/client-bedrock-agentcore` and `@aws-sdk/client-bedrock-agentcore-control`) directly. This means managing two separate clients, knowing which operations belong to which plane, and writing their own polling/pagination helpers for common workflows like waiting for memory creation or retrieving conversation turns.

## Acceptance Criteria

- [ ] Customers can create, read, update, and delete memories
- [ ] Customers can create events, list events, and retrieve memory records
- [ ] Integration tests run in CI against a real AgentCore Memory resource
- [ ] Module is exported from the package and documented with usage examples