ExecProcessReturning is unexpectedly called twice for psql request causing overflow error

[hopebo]

Description

In community postgresql, ExecProcessReturning is called once after the
main process of ExecInsert. But due to some merging errors related to
Babelfish and T-SQL, this function is wrongly called twice for psql
requests. At the first call, the xmax is not initialized causing
unexpected error raising.

The first intention of these pieces of codes is to call it in the
first place only for T-SQL(CR-52326143). And then got wrongly
cherry-picked in CR-57250041. Finally, the condition check gets
removed in CR-65026879. We should keep the first intention of the
codes, which also makes it consistent with the behaviour in
ExecUpdate.

Task: BABEL-5343

Issues Resolved

Unexpected error raised for psql requests

CREATE TABLE table1(id SERIAL, col1 VARCHAR UNIQUE);
postgres=# INSERT INTO table1 VALUES (default, 'alma')  RETURNING xmax::text::int;
ERROR:  value "4294967295" is out of range for type integer

Tests

All BabelExtension tests have passed in babelfish-for-postgresql/babelfish_extensions#3189, except one upgrade test failed due to HTTP error.

Postgres regression tests in parallel schedule passed.

Check List

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