Feat: K8 operator authentication methods

[DanielHougaard]

Description 📣

This PR adds support for all current Machine Identity authentication methods. We're also introducing some smaller structural changes to make the code scale with the new authentication methods. The authentication is primarily handled by our new official Go SDK. In the operator itself we've added a new method for deciding which auth strategy to use based on the users InfisicalSecret configuration.

Some smaller changes and remarks:

1. We're now using the Go SDK to fetch secrets when a Machine Identity auth method is being used.
2. We're now manually computing the E Tag on client-side as the Go Lang SDK doesn't have support for this (intentionally)
3. The same function is used for all secrets fetching when the authentication method is of Machine Identity type. When we eventually deprecate service tokens & service account's, we can fully depend on a single function for secret fetching, regardless of the authentication method used.

Type ✨

• Bug fix
• New feature
• Breaking change
• Documentation

---

• I have read the contributing guide, agreed and acknowledged the code of conduct. 📝

[maidul98]

Left some comments on the pr. I also left suggestions for the k8s auth in slack (you are already working on those)

[maidul98]

lgtm