Speed up playlist manifest generation

[cjcolvar]

Resolves #5496

This handles low hanging fruit by reducing solr calls by:

• Fetching all MasterFiles backing playlist items in a single SpeedyAF::Base.where
• Using #secure_stream_infos to avoid multiple sql calls for stream tokens
• Performing cannot? :read checks on parent MediaObjects to optimize case where multiple playlist items come from the same MediaObject

With these changes a 125 section playlist manifest generation time dropped from about 60 seconds to 8-10 seconds. Still slow but a big improvement. Playlist view page renders very quickly <1s so I didn't look into optimizing it at all.

Future optimizations could include:

• Leveraging bulk SpeedyAF calls and the SpeedyAF proxies to avoid solr calls in test_edit and test_read in the Ability
• Fetch all of the markers for the playlist in a single SQL call
• Optimize (possibly via memoization) active_annotation parsing of RDF for source, start_time, and end_time of AvalonAnnotations

[masaball]

Looks good!