Using IndexedScore as part of the search pre-filtering.

[isoos]

• Part of the split of Reduce the memory allocation during search with mutable IndexedScore. #8225, but also extends the use of IndexedScore into pre-filtering.
• The package name prefix check uses the packageNameLowerCased to calculate the lower-cased names only a single time (at least while the index is alive).
• The filtering uses the _documents array with indexed access instead of the Map lookup.
• The filtering won't update the Set of package names at each step, instead uses the mutable list of values. This list will be used to also drive the text search in Reduce the memory allocation during search with mutable IndexedScore. #8225.
• The TokenIndex is also updated to partially use the new IndexedScore.