Import a Devfile on a disconnected cluster with a proxy doesn’t work

Description of problem:
Users on a disconnected cluster with a proxy could not import a Devfile (from GitHub).

The API call /api/devfile/ takes 30 seconds until it fails with 504 Gateway timeout.

Version-Release number of selected component (if applicable):
This might happen since 4.8

Tested this yet only on 4.12.0-0.nightly-2022-09-07-112008

How reproducible:
Always

Steps to Reproduce:

1. Start a disconnected cluster with a proxy
2. Open the browser network inspector and filter for /api/devfile
3. Switch to Developer perspective
4. Navigate to Add > Developer Catalog (All Services) > Devfiles
5. Select a Devfile like Basic Go (https://github.com/devfile-samples/devfile-sample-go-basic.git)
6. Press Create

Actual results:

• Network call fails after 30 seconds
• Import doesn't work

Expected results:

• Import should create a Deployment and switch to topology view

Additional info:
The console Pod log contains this error:

E0909 10:28:18.448680 1 devfile-handler.go:74] Failed to parse devfile: failed to populateAndParseDevfile: Get "https://registry.devfile.io/devfiles/go": context deadline exceeded (Client.Timeout exceeded while awaiting headers)