test(wpt): update expectations for Cache.keys()
Implementing Cache.keys() flips a number of WPT subtests from failing to
passing:
- service-workers/cache-storage/cache-keys.* (now mostly passing; the
ignoreSearch/ignoreMethod/ignoreVary and VARY-listing subtests remain
expected failures as those options are not implemented)
- service-workers/idlharness.* keys() interface checks
- fetch/api/abort/cache.* (these assert signals are not stored, using
cache.keys() to read back the cached requests)
