Respect proxy settings and set http timeout in login and ssh commands

[pmatseykanets]

Ref: rancher/rancher#48321

Dedicated http clients in login and ssh commands that downloads certs and an ssh key respectively currently don't respect proxy settings and don't set http timeout.

This PR fixes that and makes use of Norman's API Client Timeout and ProxyURL options and makes it possible to specify those in the server config.

[pmatseykanets]

We probably don't need a finer precision for this. Thus *Seconds.

[alegrey91]

LGTM

[pmatseykanets]

FYI Can't use t.Parallel() because of t.Setenv().

[crobby]

lgtm. Tests seem reasonable.
Should link the issue

[pmatseykanets]

Should link the issue

Apparently we never had one, so I opened a new one.

[pmatseykanets]

Start local proxy

mitmproxy -p 8088

Set proxy and run rancher cli

export http_proxy='localhost:8088'
export https_proxy='localhost:8088'

rancher cluster ls
CURRENT   ID             STATE     NAME         PROVIDER   NODES     CPU       RAM            PODS
*         c-m-tbgzfbgf   active    downstream   K3S        1         0.55/12   0.32/7.65 GB   12/110
          local          active    local        K3S        1         0.20/12   0.14/7.65 GB   11/110