feat: Add proxy support to CLI API client

[shimako55]

Fixes #10794

Motivation

Issue:
In the current version of Argo Workflows, the API client does not function properly in environments that use a proxy server.

Purpose:
This PR aims to modify the Argo Workflows API client to ensure it functions correctly when routing through a proxy server.

Modifications

Summary of Changes:
Made modifications in cmd/argo/commands/client/conn.go, pkg/apiclient/apiclient.go, pkg/apiclient/http1-client.go, and pkg/apiclient/http1/facade.go.

Specific Changes:
Added proxy functionality using http.ProxyURL.
Integrated new proxy settings into the API client construction process.
Added proxy settings to the configuration of http.Client and http.Transport.

Reason for Changes:
To support the operation of the API client in proxy environments.

Verification

Testing Method:
Conducted manual tests in an environment with a configured proxy server.

Test Results:
Confirmed that the API client operates correctly when routing through a proxy.

Reproduction Steps:
Replace http://example.com:8080 with your actual proxy server URL in the following commands:

$ ./argo template list --proxy-url=http://example.com:8080

NAME
awesome-tiger

or

$ export HTTPS_PROXY=http://example.com:8080
$ ./argo template list

NAME
awesome-tiger

[isubasinghe]

Can you add some tests in apiclient_test.go and facade_test.go? Thanks

[shimako55]

Okay, thanks. I'll give it a try. However, it might take me some time.

[shimako55]

@isubasinghe
I have added facade_test.go.
I didn't know what tests were expected for apiclient_test.go. Could you please tell me specifically what kind of tests are expected?

[Joibel]

As suggested by @monaka, closing as implemented by #12867.

[Joibel]

Oops, this isn't implemented there.