Array directory: write queries should open in schema only mode. (#3204)
Array directory: write queries should open in schema only mode. (#3204)

Write queries only need to access the array schema from the array
directory so when opening the array in write mode, ArrayDirectory should
be set to ArrayDirectoryMode::SCHEMA_ONLY.

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TYPE: IMPROVEMENT
DESC: Array directory: write queries should open in schema only mode.
TileDB-Inc/TileDB,TileDB-Inc/TileDB,TileDB-Inc/TileDB,TileDB-Inc/TileDB