## What does this PR do?
This PR prepares for removing `httpx`, and reverts back to `requests`.
## Why is this change important?
`httpx` hasn't proven itself to be faster or better than `requests`. On the other
hand it has caused issues on Windows.
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Please update your environment to use requests instead of httpx.
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The new url parameter "timeout_limit" set timeout limit defined in second.
Example "timeout_limit=1.5" means the timeout limit is 1.5 seconds.
In addition, the query can start with <[number] to set the timeout limit.
For number between 0 and 99, the unit is the second :
Example: "<30 searx" means the timeout limit is 3 seconds
For number above 100, the unit is the millisecond:
Example: "<850 searx" means the timeout is 850 milliseconds.
In addition, there is a new optional setting: outgoing.max_request_timeout.
If not set, the user timeout can't go above searx configuration (as before: the max timeout of selected engine for a query).
If the value is set, the user can set a timeout between 0 and max_request_timeout using
<[number] or timeout_limit query parameter.
Related to #1077
Updated version of PR #1413 from @isj-privacore
Noémi Ványi
Alexandre Flament
Marc Abonce Seguin
Adam Tauber
marc