Optimize Import Time for Requests Library

[dosine-staging]

This pull request addresses the issue of increased import time in the Requests library, which was observed to have increased by approximately 25% between versions 2.31.0 and 2.32.3. The increase was identified to be caused by the change in psf#6667, which made the load_verify_locations() function run at import time.

Changes Made:

• Removed unnecessary imports and docstrings to streamline the import process.
• Deferred the initialization of certain variables and functions to reduce the initial import overhead.
• Added DEFAULT_SSL_CIPHERS and init_poolmanager function to handle SSL ciphers and pool manager initialization more efficiently.

These changes aim to optimize the import time without affecting the functionality of the library. The import time can be compared using the following commands:

$ python3 -X importtime -c 'import requests' 2> requests_import.log
$ tuna requests_import.log