dynamic dispatch seems to be really expensive, move the buffer in front of the dynamic dispatch, to reduce the number of calls into the dynamic dispatched collector.
* Adding a write schema to columnar's merge operations.
* Added unit test checking min/max when columns are empty.
* CR comment
* Rename to value_type_to_column_type
`ColumnValues` wrongly located in column_values/column.rs due to
historical reason moves to column_values/mod.rs
u128 stuff gets its own directory like u64 stuff.
* Improvement on the scalar / random bitpacker code.
Added proptesting
Added simple benchmark
Added assert and comments on the very non trivial hidden contract
Remove the need for an extra padding.
The last point introduces a small performance regression (~10%).
* Fixing unit tests
Introduced asymetric OptionalCodec / SerializableOptionalCodec
Removed cardinality from the columnar sstable.
Added DynamicColumn
Reorganized all files
Change DenseCodec serialization logic.
Renamed methods to rank/select
Moved versioning footer to the columnar level
