Add QianFan model client

[mxsl-gr]

Hi, this PR is add QianFan model client and has passed unit testing.

I can provide my api_key if needed for testing

the PR content:

• chat client
• embedding client
• spring starter
• unit test
• chat client documents
• embedding client documents

For some reasons, products from OpenAI and others can't be directly used in Chinese Mainland.

QianFan is a big model platform, A variety of models are offered, among which ERNIE Speed and ERNIE Lite are fully free. Although their API design is quite strange.

the link: QianFan

If they can supported, it will further aid spring-ai to promotion in Chinese Mainland.

If necessary, I can take care of subsequent maintenance since I'm currently using them.

The DeepSeek PR is #702
The Moonshot PR is #596

[mxsl-gr]

update content:

• add unit test
• add image client
• add image documents
• model client refactor
• squash commits.