feat: Edit the requests configuration pool_maxsize variable when initializing client

- Algolia Client Version: 2.4.0
- Language Version: Python 3.9.1

### Description
I'm replicating a dataset (60k records) with 100 threads (Python's builtin _ThreadExecutor_) at a time. And I find that from time to time I keep getting these warnings from the 'requests' library: **"Connection pool is full, discarding connection: xxxxxxxx.algolia.net"**.

The ability to edit the _pool_maxsize_ configuration variable when initializing the search client would solve this kind of issues, perhaps even allowing to edit other _requests_ configurations.

### Steps To Reproduce
Initialize a ThreadExecutor of 100 max workers.
Create a function that uses 'save_object' to store a record in a predefined index.
Loop through thousands of records, for each record:
-Add the function that saves the record with the record data to the executor

You should get the warning every ~1000 records.

Comienza en la ruta de inicialización del cliente de búsqueda y rastrea cómo se configura su sesión de requests o su pool de conexiones. Verifica cómo las llamadas concurrentes a save_object utilizan esa configuración; se considera terminado cuando los llamadores pueden establecer pool_maxsize al crear el cliente y la reproducción con 100 workers ya no emite la advertencia de pool lleno.

Escrito por el modelo de indexación a partir del texto del issue.