feature:add Wenxin model client

[lvchzh]

trafficstars

Hi, this PR is add Wenxin 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

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.