The descriptor in question is used to parse sstable's file path and return back the result. Parser, among "relevant" info, also parses sstable directory and keyspace+table names. However, there are no code (almost) that needs those strings. And the need to construct descriptor with those makes some places obscurely use empty strings.
The PR removes sstable's directory, keyspace and table names from descriptor and, while at it, relaxes the sstable directory code that makes descriptor out of a real sstable object by (!) parsing its Data file path back.
Closesscylladb/scylladb#15617
* github.com:scylladb/scylladb:
sstables: Make descriptor from sstable without parsing
sstables: Do not keep directory, keyspace and table names on descriptor
sstables: Make tuple inside helper parser method
sstables: Do not use ks.cf pair from descriptor
sstables: Return tuple from parse_path() without ks.cf hints
sstables: Rename make_descriptor() to parse_path()
96787ec0a5