Adds a new platform interface for matching and comparing platforms.
This new interface allows both filtering and ordering of platforms
to support running multiple platform and choosing the best platform.
Signed-off-by: Derek McGowan <derek@mcgstyle.net>
This makes it easier for callers to call this function and populate the
config without relying on specific flags across commands.
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
Separate Fetch and Pull commands in client to distinguish
between platform specific and non-platform specific operations.
`ctr images pull` with all platforms will now unpack all platforms.
`ctr content fetch` now supports platform flags.
Signed-off-by: Derek McGowan <derek@mcgstyle.net>
