For PostgreSQL::Test compatibility, alias entire package symbol tables.

Remove the need to edit back-branch-specific code sites when
back-patching the addition of a PostgreSQL::Test::Utils symbol.  Replace
per-symbol, incomplete alias lists.  Give old and new package names the
same EXPORT and EXPORT_OK semantics.  Back-patch to v10 (all supported
versions).

Reviewed by Andrew Dunstan.

Discussion: https://postgr.es/m/20220622072144.GD4167527@rfd.leadboat.com

src/test/perl/PostgreSQL/Test/Utils.pm

@@ -1,48 +1,16 @@
 # Copyright (c) 2022, PostgreSQL Global Development Group
 
-# allow use of release 15+ perl namespace in older branches
-# just 'use' the older module name.
-# We export the same names as the v15 module.
-# See TestLib.pm for alias assignment that makes this all work.
+# Allow use of release 15+ Perl package name in older branches, by giving that
+# package the same symbol table as the older package.
 
 package PostgreSQL::Test::Utils;
 
 use strict;
 use warnings;
 
+use TestLib;
+BEGIN { *PostgreSQL::Test::Utils:: = \*TestLib::; }
+
 use Exporter 'import';
 
-use TestLib;
-
-our @EXPORT = qw(
-  generate_ascii_string
-  slurp_dir
-  slurp_file
-  append_to_file
-  check_mode_recursive
-  chmod_recursive
-  check_pg_config
-  dir_symlink
-  system_or_bail
-  system_log
-  run_log
-  run_command
-  pump_until
-
-  command_ok
-  command_fails
-  command_exit_is
-  program_help_ok
-  program_version_ok
-  program_options_handling_ok
-  command_like
-  command_like_safe
-  command_fails_like
-  command_checks_all
-
-  $windows_os
-  $is_msys2
-  $use_unix_sockets
-);
-
 1;