Revert support for improved tracking of nested queries

This commit reverts the two following commits:
- 499edb0974, track more precisely query locations for nested
statements.
- 06450c7b8c, a follow-up fix of 499edb0974 with query locations.
The test introduced in this commit is not reverted.  This is proving
useful to track a problem that only pgaudit was able to detect.

These prove to have issues with the tracking of SELECT statements, when
these use multiple parenthesis which is something supported by the
grammar.  Incorrect location and lengths are causing pg_stat_statements
to become confused, failing its job in query normalization with
potential out-of-bound writes because the location and the length may
not match with what can be handled.  A lot of the query patterns
discussed when this issue was reported have no test coverage in the main
regression test suite, or the recovery test 027_stream_regress.pl would
have caught the problems as pg_stat_statements is loaded by the node
running the regression tests.  A first step would be to improve the test
coverage to stress more the query normalization logic.

A different portion of this work was done in 45e0ba30fc, with the
addition of tests for nested queries.  These can be left in the tree.
They are useful to track the way inner queries are currently tracked by
PGSS with non-top-level entries, and will be useful when reconsidering
in the future the work reverted here.

Reported-by: Alexander Kozhemyakin <a.kozhemyakin@postgrespro.ru>
Discussion: https://postgr.es/m/18947-cdd2668beffe02bf@postgresql.org

contrib/pg_overexplain/expected/pg_overexplain.out

@@ -37,7 +37,7 @@ EXPLAIN (DEBUG) SELECT 1;
    Subplans Needing Rewind: none
    Relation OIDs: none
    Executor Parameter Types: none
-   Parse Location: 16 for 8 bytes
+   Parse Location: 0 to end
 (11 rows)
 
 EXPLAIN (RANGE_TABLE) SELECT 1;
@@ -119,7 +119,7 @@ $$);
    Subplans Needing Rewind: none
    Relation OIDs: NNN...
    Executor Parameter Types: none
-   Parse Location: 41 to end
+   Parse Location: 0 to end
  RTI 1 (relation, inherited, in-from-clause):
    Eref: vegetables (id, name, genus)
    Relation: vegetables
@@ -240,7 +240,7 @@ $$);
        <Subplans-Needing-Rewind>none</Subplans-Needing-Rewind>      +
        <Relation-OIDs>NNN...</Relation-OIDs>                        +
        <Executor-Parameter-Types>none</Executor-Parameter-Types>    +
-       <Parse-Location>53 to end</Parse-Location>                   +
+       <Parse-Location>0 to end</Parse-Location>                    +
      </PlannedStmt>                                                 +
      <Range-Table>                                                  +
        <Range-Table-Entry>                                          +
@@ -344,7 +344,7 @@ $$);
    Subplans Needing Rewind: none
    Relation OIDs: NNN...
    Executor Parameter Types: none
-   Parse Location: 28 to end
+   Parse Location: 0 to end
 (37 rows)
 
 SET debug_parallel_query = false;
@@ -372,7 +372,7 @@ $$);
    Subplans Needing Rewind: none
    Relation OIDs: NNN...
    Executor Parameter Types: 0
-   Parse Location: 28 to end
+   Parse Location: 0 to end
 (15 rows)
 
 -- Create an index, and then attempt to force a nested loop with inner index
@@ -436,7 +436,7 @@ $$);
    Subplans Needing Rewind: none
    Relation OIDs: NNN...
    Executor Parameter Types: 23
-   Parse Location: 75 for 62 bytes
+   Parse Location: 0 to end
 (47 rows)
 
 RESET enable_hashjoin;