Merge branch 'bp/read-cache-parallel'

A new extension to the index file has been introduced, which allows the file to be read in parallel. * bp/read-cache-parallel: read-cache: load cache entries on worker threads ieot: add Index Entry Offset Table (IEOT) extension read-cache: load cache extensions on a worker thread config: add new index.threads config setting eoie: add End of Index Entry (EOIE) extension read-cache: clean up casting and byte decoding read-cache.c: optimize reading index format v4