Registry library needs to support accessing devfiles over a proxy

[johnmcollier]

On airgapped clusters (where access to https://registry.devfile.io might only be available through a proxy), requests via the registry-library fail with:

E0722 21:04:27.064568 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": dial tcp 34.198.81.130:443: i/o timeout (Client.Timeout exceeded while awaiting headers)
E0722 21:04:47.088332 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
E0722 21:05:10.543965 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": dial tcp 34.198.81.130:443: i/o timeout (Client.Timeout exceeded while awaiting headers)
E0722 21:05:30.558814 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
E0722 21:06:07.005139 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
E0722 21:06:27.017406 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
E0722 21:09:40.999418 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
E0722 21:09:57.396735 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
E0722 21:10:01.024051 1 devfile-handler.go:40] Failed to read from registry https://registry.devfile.io/: Get "https://registry.devfile.io/index/sample": context deadline exceeded (Client.Timeout exceeded while awaiting headers)

The registry library needs to honour any existing proxy configurations that are passed in through the container's environment variable (HTTP_PROXY, HTTPS_PROXY)

/area registry
/kind bug

[kim-tsao]

The fix can be entirely contained in the registry library and includes all affected APIs, not just the one that console calls. Once this package is updated, I'll make the dependency change on the console side.