Retry sp http requests on network error

[hugomrdias]

We should retry SP request on network error.

Currently some already do retries for other reasons and should also retry for network errors since the latest iso-web release, but we should verify the current retry logic doesnt override the default retry on network error.

Some other requests do not retry and can benefit from simple retry on network error.

related:

• fix(synapse-core): retry upload session creation on transient network failures #725