Warn on any command if not on latest version

[courier-new]

Many users encounter bugs from outdated versions of src-cli and raise them to support before realizing they were already fixed and just needed to update. Recently, a user hit a nasty bug when they were unintentionally running a version 16 months out of date! We should try to warn users if the version of src-cli they are running is not at or above the version recommended by their Sourcegraph instance (/.api/src-cli/version). We already perform this check when running src version:

> src version
Current version: 4.3.0
Recommended version: 4.4.0 or later

We should perform this check before running any command and highlight a warning in the output if it's out-of-date.

[courier-new]

This feels like a quick UX win but also not one that's immediately needed, so maybe backlog.