Issue #3613515 by lindsay.wils, sriram_s: Use SearchApiCachePluginTrait in...

SearchApiTimeTagCache extends core's Time but does not use SearchApiCachePluginTrait, unlike its two siblings. Both cacheSet() and cacheGet() fall through to core, which knows nothing about Search API's ResultSet, so on a cache hit getSearchApiResults() returns empty and facets render nothing. Adding the trait matches SearchApiTimeCache.

testCachedResultSetIsRestored() covers all three caching plugins. Without the fix it fails on the time_tag data set only. The existing testDisplayCacheability() passes with the bug present because it only asserts the results cache is populated, not that the cached ResultSet survives.

Closes #3613515