[#23094] YSQL: Fix flaky test TestPgRegressFeaturePartition

Summary:
The test became flaky after commit 7c8343d fixed the logic for cascaded drops on columns.

The test yb_feature_hash_types creates a domain and creates a table with a key column that has the domain as its type. However, since we currently don't support key column drops (#22902), the test fails when the cleanUpCustomEntities() function in BasePgSQLTest.java attempts to drop the domain (that has the key column as a dependant object) during cleanup.
Moreover, the test is flaky because sometimes the table may be dropped before the domain, as the order of the drops depends on the pg_depend scan output, which isn't deterministic because pg_depend doesn't have a primary key and internally uses ybctid.

Fix the test flakiness by dropping the table in yb_feature_hash_types before the test clean up logic.
Jira: DB-12029

Test Plan: ./yb_build.sh --java-test 'org.yb.pgsql.TestPgRegressFeaturePartition' -n 20

Reviewers: myang

Reviewed By: myang

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D36329

src/postgres/src/test/regress/expected/yb_feature_hash_types.out

@@ -119,6 +119,10 @@ ERROR:  PRIMARY KEY containing column of type 'user_defined_type' not yet suppor
 -- Domain Types
 CREATE DOMAIN feature_h_domain AS INTEGER CHECK (VALUE > 0);
 CREATE TABLE ft_h_tab_domain (feature_col feature_h_domain PRIMARY KEY);
+-- YB(fizaa): Work-around for the test cleanup code that drops the domain.
+-- Dropping the domain will cause an error because a key column depends on it (GH #22902).
+-- By dropping the table now, the clean up code will succeed.
+DROP TABLE ft_h_tab_domain;
 --
 -- Object Identifier Types
 CREATE TABLE ft_h_tab_oid (feature_col OID PRIMARY KEY);

src/postgres/src/test/regress/sql/yb_feature_hash_types.sql

@@ -95,6 +95,10 @@ CREATE TABLE ft_h_tab_range (feature_col feature_h_range PRIMARY KEY);
 -- Domain Types
 CREATE DOMAIN feature_h_domain AS INTEGER CHECK (VALUE > 0);
 CREATE TABLE ft_h_tab_domain (feature_col feature_h_domain PRIMARY KEY);
+-- YB(fizaa): Work-around for the test cleanup code that drops the domain.
+-- Dropping the domain will cause an error because a key column depends on it (GH #22902).
+-- By dropping the table now, the clean up code will succeed.
+DROP TABLE ft_h_tab_domain;
 --
 -- Object Identifier Types
 CREATE TABLE ft_h_tab_oid (feature_col OID PRIMARY KEY);