[httpx] Improper Input Validation in httpx

Encode OSS httpx <=1.0.0.beta0 is affected by improper input validation in httpx.URL, httpx.Client and some functions using httpx.URL.copy_with.
References

https://nvd.nist.gov/vuln/detail/CVE-2021-41945
https://github.com/encode/httpx/issues/2184