patch: Added support for passing params as keyword arg

[MateuszOssGit]

Added support for passing params as keyword arg

• init:

chat = ChatWatsonx(
    model_id=MODEL_ID_TOOL,
    url=URL,
    project_id=WX_PROJECT_ID,
    max_tokens=10
)

• method:

resp_1 = chat.invoke(prompt_1, max_tokens=10)

[Mateusz-Switala]

Can we somehow reuse here _update_params function?

[MateuszOssGit]

Probably it can not be reused. Here we are updating the default parameters, but in _update_params function (renamed to _merge_params ) we are only merge it without adding it to default params.

[MateuszOssGit]

Integration test passing successfully -> https://github.com/langchain-ai/langchain-ibm/actions/runs/11741957098

[Mateusz-Switala]

LGTM