AI integration deep proxies return new function references on every property access

The `get` trap in AI integration deep proxies always returns a different value instead of memoizing bound/instrumented methods.

For example, `console.log(ai.run === ai.run)` prints `false` because each access creates a new function via `instrumentMethod(...)` or `value.bind(obj)`.

This pattern exists across multiple AI integrations:

- `packages/core/src/tracing/openai/index.ts` (`createDeepProxy`)
- `packages/core/src/tracing/anthropic-ai/index.ts` (`createDeepProxy`)
- `packages/core/src/tracing/google-genai/index.ts` (`createDeepProxy`)

Suggested fix: keep a `Map` in the closure to store bound/instrumented methods, rather than creating a new value on every `get`.

> Originally posted by @isaacs in https://github.com/getsentry/sentry-javascript/pull/22119#discussion_r3581015061

Comece em createDeepProxy em packages/core/src/tracing/openai/index.ts, packages/core/src/tracing/anthropic-ai/index.ts e packages/core/src/tracing/google-genai/index.ts. Rastreie o get trap e os caminhos de instrumentMethod ou bind e, em seguida, verifique se acessos repetidos ao mesmo método retornam a mesma referência, preservando o comportamento de instrumentação.

Escrita pelo modelo de indexação a partir do texto da issue.