add `west.check_version()` or so utility function

[mbolivar]

Add a utility routine that can be used to check if west is a minimum version, or make west's version accessible as a named tuple like sys.version_info so that it can be compared against more easily.

[tejlmand]

Specifying the version required in the call allows for a common error message across all modules / extension commands that requires a specific version. Also each user of west does not need to parse the version themselves.

Thus I favor this over a sys.version_info style feature.

[mbolivar]

In that case I would argue for a WestCommand.ensure_version() method.