Replace retry-request with gaxios

[retry-request](https://github.com/googleapis/retry-request) was deprecated in July 2024 and has been replaced by [gaxios](https://github.com/googleapis/gaxios).

Any chance that you can migrate the `retry-request` dependency?

Motivation: The redundant `@types/request@2.48.12` sub-dependency conflicts with one of the Jest 30.x sub-dependencies and makes an upgrade to Jest 30.x challenging.

```
└─┬ @google-cloud/common@6.0.0
└─┬ retry-request@8.0.0
└── @types/request@2.48.12
```