http-cache

replace cacache with redb + tokio::fs in StreamingManager, preserve multi-valued headers on revalidation, fix surf/ureq example panic

consolidate streaming cache orchestration into core, fix some RFC 7234 compliance issues, refactor Tower adapter to use HttpCache::run

misc cleanup

bump versions and update changelogs

remove async_trait, fix duplicate headers on revalidation in ureq, lower deserialization failure logs to debug