Show package counts / info when scanning SBOM

[kzantow]

What would you like to be added: Add a TUI element when using an SBOM source (or package urls/etc.) that indicates how many packages were read.

Why is this needed: When scanning an image or directory, there are TUI elements indicating how many packages were cataloged, but nothing is displayed when scanning an SBOM (unless using -vvv). The problem is: in the event that there are no vulnerabilities, there is no indication Grype actually scanned anything and it could be confusing to the end user if Grype actually did anything. By adding the feedback about how many packages were read, this should be more clear.