fix: Typehint the Stream class and fix deprecated interface HttpClient

[tarekdj]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Related tickets
Documentation
License	MIT

What's in this PR?

• Fix the type hinting of Stream class in order to make it compatible with StreamInterface
• Replace depreacted interface HttpClient

Why?

Fix the compatibility of Stream class with the StreamInterface

Checklist

• Updated CHANGELOG.md to describe BC breaks / deprecations | new feature | bugfix
• Documentation pull request created (if not simply a bugfix)

To Do

• Update CHANGELOG.md

[dbu]

we could switch this client to be a PSR-18 client. but that would mean somebody would need to commit to maintain this client. there are a bunch of http clients around: symfony, guzzle, buzz, the php-http/curl-client and some others.

is there value in keeping the socket client alive?

[dbu]

if we decide to keep this maintained, we should adjust the socket-client.rst page in the documentation, reverting php-http/documentation#310 (comment) and maybe add more information.