doc: Clarify log level for VERBOSE messages in maintenance commands.

VERBOSE messages from ANALYZE, CLUSTER, REINDEX, and VACUUM are logged
at the INFO level, but this detail was missing from the documentation.
This commit updates the docs to mention the log level for these messages.

Author: Masahiro Ikeda
Reviewed-by: Yugo Nagata
Discussion: https://postgr.es/m/b4a4b7916982dccd9607c8efb3ce5116@oss.nttdata.com

doc/src/sgml/ref/analyze.sgml

@@ -65,7 +65,7 @@ ANALYZE [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <r
     <term><literal>VERBOSE</literal></term>
     <listitem>
      <para>
-      Enables display of progress messages.
+      Enables display of progress messages at <literal>INFO</literal> level.
      </para>
     </listitem>
    </varlistentry>

doc/src/sgml/ref/cluster.sgml

@@ -106,7 +106,8 @@ CLUSTER [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <r
     <term><literal>VERBOSE</literal></term>
     <listitem>
      <para>
-      Prints a progress report as each table is clustered.
+      Prints a progress report as each table is clustered
+      at <literal>INFO</literal> level.
      </para>
     </listitem>
    </varlistentry>

doc/src/sgml/ref/reindex.sgml

@@ -194,7 +194,8 @@ REINDEX [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] { DA
     <term><literal>VERBOSE</literal></term>
     <listitem>
      <para>
-      Prints a progress report as each index is reindexed.
+      Prints a progress report as each index is reindexed
+      at <literal>INFO</literal> level.
      </para>
     </listitem>
    </varlistentry>

doc/src/sgml/ref/vacuum.sgml

@@ -129,7 +129,8 @@ VACUUM [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <re
     <term><literal>VERBOSE</literal></term>
     <listitem>
      <para>
-      Prints a detailed vacuum activity report for each table.
+      Prints a detailed vacuum activity report for each table
+      at <literal>INFO</literal> level.
      </para>
     </listitem>
    </varlistentry>