Limit "az extension add --upgrade" only to upgrades within major version of extension

**Is your feature request related to a problem? Please describe.**

We're relying on `az extension add --upgrade` to keep extensions up-to-date for our tooling.

Unfortunately, this may result in issues like #18027.

**Describe the solution you'd like**

Right now the choice for `az extension add --upgrade` is limited between a pinned version or a latest version. That'd be great to have another option (e.g., "latestWithinMajor" or support [semver ranges notation](https://docs.npmjs.com/cli/v6/using-npm/semver#advanced-range-syntax)) for an "--upgrade" operation.

**Describe alternatives you've considered**

Currently we had to pin the version of resource-graph extension with a note to upgrade to a new format of response ASAP.