New search system is based on a Radix Tree. The Radix Tree contains a shallow list of all decl names (ie no paths), plus some suffixes, split by following the official style guide (eg "HashMapUnmanaged" also produces "MapUnmanaged" and "Unmanaged", same with snake_case and camelCase names).
Additionally, the search system uses the decl graph data to recognize hierarchical relationships between decls, allowing you to zero on a target namespace for search. As an example "fs create" will score highe all things related to the creation of files and directories inside of `std.fs`, while still showing (but with lower score) matches from `std.Bulild`.
As another example "fs windows" will prioritize windows-related results in `std.fs`, while "windows fs" will prioritize fs-related results in `std.windows`.
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