enhance facter filtering capabilities

[vchepkov]

Please consider adding more filtering capabilities to facter.

Consider the following use cases:

• large structured fact sub-trees, like rhsm.enabled_repo_ids
• sensitive data inside a structured fact, like gce.instance.project.attributes.ssh-keys
• facts based on values, like mountpoints /var/lib/docker/overlay*
• exclude values, everything except cpuinfo.0 (see filter cpuinfo #2677)

The feature was previously requested in archive project https://puppet.atlassian.net/browse/FACT-769

[tvpartytonight]

Potential spot for addressing this could be here.