[Phase 1][YSQL][Tablegroups] Partitioned tables do not inherit tablegroup

[frozenspider]

Jira Link: DB-2800

Description

When you create a PARTITION BY table with TABLEGROUP, its PARTITION tables are created w/o tablegroup unless you explicitly declare it.
Example:

CREATE TABLEGROUP tg1;
CREATE TABLE prt (id int PRIMARY KEY, v int) PARTITION BY RANGE (id) TABLEGROUP tg1;
CREATE INDEX prt_idx ON prt (v);

CREATE TABLE prt_p1 PARTITION OF prt FOR VALUES FROM (1) TO (4);
CREATE TABLE prt_p2 PARTITION OF prt FOR VALUES FROM (5) TO (9) TABLEGROUP tg1;

\dgrt
                 List of tablegroup tables
 Group Name | Group Owner |     Name     | Type  |  Owner
------------+-------------+--------------+-------+----------
 tg1        | yugabyte    | prt          | table | yugabyte
 tg1        | yugabyte    | prt_idx      | index | yugabyte
 tg1        | yugabyte    | prt_p2       | table | yugabyte
 tg1        | yugabyte    | prt_p2_v_idx | index | yugabyte
(4 rows)