[azure-eventhubs] expand authentication options

## Context

The azure-eventhub used the connection string as the only authentication method. Connection string was the only authentication method supported by the azure-eventhub processor v1.

However, since we introduced the (azure-eventhubs) processor v2 and the [modern Event Hubs SDK](https://github.com/Azure/azure-sdk-for-go/tree/main/sdk/messaging/azeventhubs), we now have many more authentication options users can leverage to better fir their environment.

The modern Event Hubs SDK uses the [azidentity](https://pkg.go.dev/github.com/Azure/azure-sdk-for-go/sdk/azidentity) module, which supports the following authentication methods:

- Client secret
- Client certificate
- Managed Identity
- Workload Identity

## Goal

Extend the azure-eventhub processor v2 by adding the following authentication options:

| Auth | Beats (PR) | Integrations (PR) | Versions |
|--------|--------|--------|--------|
| Client secret | ✅ https://github.com/elastic/beats/pull/47256 | 👷 https://github.com/elastic/integrations/issues/17030 | 8.19.10, 9.1.10, 9.2.4, or later. |
| Client certificate ||||
| Managed Identity | 👷 https://github.com/elastic/beats/pull/48655 | ||
| Workload Identity ||||

## Impact

By adding widely used solutions like Client Secret and Managed Identity, we’ll allow the azure-eventhub processor to fit a broader range of deployment scenarios.