Add support for Azure OpenAI models and managed identity auth

[jgbradley1]

Motivation

It is challenging to get started with using opencompass on Azure OpenAI models and to specify the reasoning level when using reasoning models.

Modification

This PR adds support (with examples) for models hosted in Azure OpenAI. Support for managed identity authentication has been added for users unable to provide an API key as well as an (optional) configuration parameter to control the reasoning_effort when reasoning models are used.

BC-breaking (Optional)

None

Use cases (Optional)

Direct support for any models hosted in Azure OpenAI is now enabled.

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects.
• CLA has been signed and all committers have signed the CLA in this PR.