fix(config): retry fetching extensions on failure

[DanielSLew]

Summary

Retry fetch to get extensions from jigsaw. If this call fails the build will fail.

Jigsaw calls BB, and we see that there's the occasionally blip in the request there, so this will make fetching extensions succeed more consistently.

[serhalp]

btw @DanielSLew we just fixed main a minute ago, just rebase!