feat: Update the Gemini API call method and add embedding-001 model supported

[devojony]

close #868

我已确认该 PR 已自测通过，相关截图如下：

curl --location --request POST 'http://localhost:3000/v1/embeddings' \
--header 'User-Agent: Apifox/1.0.0 (https://apifox.com)' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer sk-XXXXXXX' \
--header 'Accept: */*' \
--header 'Host: localhost:3000' \
--header 'Connection: keep-alive' \
--data-raw '{
    "input": "The food was delicious and the waiter...",
    "model": "embedding-001",
    "encoding_format": "float"
  }'

[devojony]

在这个PR上，我还需要做什么？@songquanpeng