This is a list of trivial features for Sequence (originally mentioned as part of MDEV-13005)

• Support syntax "CREATE SEQUENCE x AS <some_int_type>';
  <some_int_type> can mean all the integers that we support
  Currently (as per documentation) maximum value that sequence can support is 9223372036854775806.
  But unsigned bigint can have maximum (unsigned) value: 18446744073709551615
  So adding support for this maximum (unsigned) value is needed.
  Also, set maximum minimum based on the datatype

• Allow in parser very big numbers (decimal) for MAXVALUE but change these to LONGLONG_MAX-1, with a note for the user. This is needes as it's common practice to use
  MAXVALUE 9999999999999999999999999999 in Oracle examples.

• Create information_schema.sequences that lists all sequences and their information. Should work similar to views:
  select * from information_schema.sequences where table_schema="test";
  The column names are:
  SEQUENCE_CATALOG, SEQUENCE_SCHEMA, SEQUENCE_NAME, DATA_TYPE, NUMERIC_PRECISION, NUMERIC_PRECISION_RADIX, NUMERIC_SCALE, START_VALUE, MINIMUM_VALUE, MAXIMUM_VALUE, INCREMENT, CYCLE_OPTION, DECLARED_DATA_TYPE, DECLARED_NUMERIC_PRECISION, DECLARED_NUMERIC_SCALE

Some suggested values:
DATA_TYPE BIGINT
DECLARED_DATA_TYPE BIGINT
NUMERIC_PRECISION 19
NUMERIC_PRECISION_RADIX 10
DECLARED_DATA_TYPE NULL
DECLARED_NUMERIC_PRECISION NULL
DECLARED_NUMERIC_SCALE NULL