Changelog category (leave one):

• Performance Improvement

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Enable reading LowCardinality string columns from ORC.

This PR must be reviewed after #68591

1 Construct the data

set output_format_orc_dictionary_key_size_threshold = 1;
select concat('gluten ', cast(rand()%1000 as String)) from numbers(10000000) into outfile 'dict.orc' truncate;

2 Readind dict.orc and execute group by (speedup 2.6x)

set input_format_orc_dictionary_as_low_cardinality = 0; 
select "concat('gluten ', CAST(modulo(rand(), 1000), 'String'))" as x, count(1) from  file('dict.orc') group by x format Null; 
0 rows in set. Elapsed: 0.485 sec. Processed 10.00 million rows, 14.92 MB (20.63 million rows/s., 30.79 MB/s.)

set input_format_orc_dictionary_as_low_cardinality = 1; 
select "concat('gluten ', CAST(modulo(rand(), 1000), 'String'))" as x, count(1) from  file('dict.orc') group by x format Null;
0 rows in set. Elapsed: 0.190 sec. Processed 10.00 million rows, 14.92 MB (52.57 million rows/s., 78.43 MB/s.)

Documentation entry for user-facing changes

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