Alert user of new extension version is available

[wbreza]

When a user invokes a custom command azd ai agent init for example check if there is a new version of the extension available we should prompt the user if they want to upgrade.

[tg-msft]

I think we should add a check before launching an extension (when run interactively) that pings the feed to see if it's the latest version (for some definition of latest) and asks if the user wants to upgrade first. They should be able to say Upgrade, Don't Upgrade, Upgrade All Extensions (so you don't have to stub your toe on one extension after another if you open azd the day after Build), Stop asking for this extension, Stop asking for all extensions. We should have similar config options you can set globally if desired. We should also skip the check if you have an extension pinned to a specific version (which isn't well supported yet, but we want to enable for rock solid deployments). We might want a config setting for the strategy we use to define "latest version" as well because some people might want Any, Patch Only, Patch/Minor Only, ..., etc., to stay reasonably up to date without tons of noise.

[rajeshkamal5050]

@wbreza add it as part of the next set of extension updates towards GA.