kallsyms: change Modules caching strategy, cache address lookups

[ti-mo]

See individual commits for context.

At a high level:

• add caching for __ksym reference resolving
• stop caching all text symbols that have an associated kmod
• for both addresses and modules, cache only the requested symbols (pull-through cache)
• at the beginning of Collection creation, scan all ProgramSpecs and instructions for module and symbol references and request them in two batches
• perform individual symbol lookups (from the populated cache) in newProgramWithOptions onwards
• don't open /proc/kallsyms during CollectionSpec loading