Migrate to httpx2

### Confirm this is a Python library issue and not an underlying Cloudflare API issue.

- [x] This is an issue with the Python library

### Describe the bug

This project currently depends on httpx, which is no longer maintained. Given that situation, it should be migrated away to a maintained http library. One such option is `httpx2` (https://github.com/pydantic/httpx2), which seems to be the accepted community fork of httpx, specially given it's maintained by pydantic. This is even more true, when the author of `httpxyz` (a previous fork) [blesses](https://tildeweb.nl/~michiel/httpx2.html) this new package.

Note that Sentry, already added support for this package in https://github.com/getsentry/sentry-python/issues/6448.

### To Reproduce

Check the project dependencies

### Code snippets

```Python

```

### OS

any

### Python version

any

### Library version

5.x

まずプロジェクトの依存関係を確認し、httpx がどこで宣言されていて、Python ライブラリでどのように使用されているかを調べます。これらの参照をメンテナンスされている httpx2 パッケージに移行し、その後ライブラリの既存のテストスイートを実行して、依存関係の変更がサポート対象のすべての用途で機能することを確認します。

索引モデルが issue の本文から書いたものです。