Run regression tests with timezone America/Los_Angeles.

Historically we've used timezone "PST8PDT", but the recent release
2024b of tzdb changes the definition of that zone in a way that
breaks many test cases concerned with dates before 1970.  Although
we've not yet adopted 2024b into our own tree, this is already
problematic for people using --with-system-tzdata if their platform
has already adopted 2024b.  To work with both older and newer
versions of tzdb, switch to using "America/Los_Angeles", accepting
the ensuing changes in regression test results.

Back-patch to all supported branches.

Per report and patch from Wolfgang Walther.

Discussion: https://postgr.es/m/0a997455-5aba-4cf2-a354-d26d8bcbfae6@technowledgy.de

doc/src/sgml/ref/set.sgml

@@ -200,7 +200,7 @@ SELECT setseed(<replaceable>value</replaceable>);
 
        <variablelist>
         <varlistentry>
-         <term><literal>'PST8PDT'</literal></term>
+         <term><literal>'America/Los_Angeles'</literal></term>
          <listitem>
           <para>
            The time zone for Berkeley, California.
@@ -298,7 +298,7 @@ SET datestyle TO postgres, dmy;
   <para>
    Set the time zone for Berkeley, California:
 <screen>
-SET TIME ZONE 'PST8PDT';
+SET TIME ZONE 'America/Los_Angeles';
 </screen>
   </para>
 

doc/src/sgml/regress.sgml

@@ -534,11 +534,11 @@ make check NO_LOCALE=1
     <para>
      Most of the date and time results are dependent on the time zone
      environment.  The reference files are generated for time zone
-     <literal>PST8PDT</literal> (Berkeley, California), and there will be
+     <literal>America/Los_Angeles</literal>, and there will be
      apparent failures if the tests are not run with that time zone setting.
      The regression test driver sets environment variable
-     <envar>PGTZ</envar> to <literal>PST8PDT</literal>, which normally
-     ensures proper results.
+     <envar>PGTZ</envar> to <literal>America/Los_Angeles</literal>,
+     which normally ensures proper results.
     </para>
    </sect2>