Allow v6 store to support multiple qualifiers

[wagoodman]

Today the v6 store can search for singular things (a single vulnerability, filter by a single distro, search by a single package). This PR changes the store to support searching and filtering by multiple criteria (supporting #2303).

All changes made:

• add slice of all *Spec objects in searching
• allow for configurable limit on queries (default is no limit)
• fetch and attach blobs in batches (not individually)
• fetch all queries in small batches (better support for queries with several results)
• adjust indexes:
  • hydrate them when opening a writable DB without truncate options
  • adds additional individual indexes for common search cases (search by name, product, or vendor)
• fix logging and monitor values when importing/downloading a DB
• better stringer support for *Spec classes (improved logging)
• upgrade the gorm logger:
  • enable debug option
  • support setting log level
  • warn on slow queries
  • trace logging support to show individual queries

[kzantow]

what is this for? (the model docs didn't help me understand this) maybe add a comment if it's required as to why

[wagoodman]

this change was unintentional and is a no-op essentially in this context (I'll remove this change). This orients the query to be against the model (automatically inferring the table name from the model). We could in theory be using this more often to that joins are less explicit, but that can be done later.