FIX Remove aria2c dependency from HuggingFace Target

[nina-msft]

Description

Remove aria2c dependency from HuggingFace target in favor of httpx implementation of downloading files to disk. This requires usage of asyncio to handle the new async function within HuggingFaceChatTarget's constructor.

Other changes:

• Pass in attention_mask argument to model.generate() function, to address a warning: "the attention mask is not set and cannot be inferred from input because pad token is same as eos token. as a consequence, you may observe unexpected behavior."
• Address an exception that the target did not have an attribute that is defined by it's parent by adding a call to the parent's constructor

Tests and Documentation

Updated existing unit tests and ran jupytext on the HuggingFace demo notebook

[romanlutz]

Very cool!

[romanlutz]

CC @KutalVolkan

aria2c isn't available by default so we are aiming to replace it.