Add extensive test for various read settings

The following settings had been covered:
- min_bytes_to_use_direct_io
- local_filesystem_read_method
- local_filesystem_read_prefetch
- read_priority
- max_read_buffer_size

tests/queries/0_stateless/02051_read_settings.reference.j2

@@ -0,0 +1,11 @@
+{% for read_method in ['read', 'mmap', 'pread_threadpool', 'pread_fake_async'] -%}
+{% for direct_io in [0, 1] -%}
+{% for prefetch in [0, 1] -%}
+{% for priority  in [0, 1] -%}
+{% for buffer_size in [65505, 1048576] -%}
+1000000
+{% endfor -%}
+{% endfor -%}
+{% endfor -%}
+{% endfor -%}
+{% endfor -%}

tests/queries/0_stateless/02051_read_settings.sql.j2

@@ -0,0 +1,31 @@
+-- Tags: long
+--
+-- Test for testing various read settings.
+
+drop table if exists data_02051;
+
+create table data_02051 (key Int, value String) engine=MergeTree() order by key
+as select number, repeat(toString(number), 5) from numbers(1e6);
+
+{# check each local_filesystem_read_method #}
+{% for read_method in ['read', 'mmap', 'pread_threadpool', 'pread_fake_async'] %}
+{# check w/ O_DIRECT and w/o (min_bytes_to_use_direct_io) #}
+{% for direct_io in [0, 1] %}
+{# check local_filesystem_read_prefetch (just a smoke test) #}
+{% for prefetch in [0, 1] %}
+{# check read_priority (just a smoke test) #}
+{% for priority  in [0, 1] %}
+{# check alignment for O_DIRECT with various max_read_buffer_size #}
+{% for buffer_size in [65505, 1048576] %}
+select count(ignore(*)) from data_02051 settings
+    min_bytes_to_use_direct_io={{ direct_io }},
+    local_filesystem_read_method='{{ read_method }}',
+    local_filesystem_read_prefetch={{ prefetch }},
+    read_priority={{ priority }},
+    max_read_buffer_size={{ buffer_size }}
+;
+{% endfor %}
+{% endfor %}
+{% endfor %}
+{% endfor %}
+{% endfor %}