Changing the unexpected default behavior for URL + params

[jamesbraza]

With httpx==0.28.1's URL there is a footgun behavior where the params arg will clobber any params in the url string:

from httpx import URL

print(
    URL("https://httpbin.org/get?name=stub", params={"language": "python"})
)
# https://httpbin.org/get?language=python

This was also recently reported as a bug here: #3621

Why is silent clobbering the default behavior? Imo this behavior is both unexpected and hard to debug