pgsql: Reflect normalization of query strings for utilities in pg_stat_

Reflect normalization of query strings for utilities in pg_stat_statements

Applying normalization changes how the following query strings are
reflected in pg_stat_statements, by showing Const nodes with a
dollar-signed parameter as this is how such queries are structured
internally once parsed:
- DECLARE
- EXPLAIN
- CREATE MATERIALIZED VIEW
- CREATE TABLE AS

More normalization could be done in the future depending on the parts
where query jumbling is applied (like A_Const nodes?), the changes being
reflected in the regression tests in majority created in de2aca2. This
just allows the basics to work for utility queries using Const nodes.

Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/Y+MRdEq9W9XVa2AB@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/daa8365a900729fe2a8d427fbeff19e763e35723

Modified Files
--------------
contrib/pg_stat_statements/expected/cursors.out | 14 ++++-----
contrib/pg_stat_statements/expected/utility.out | 38 ++++++++++++-------------
contrib/pg_stat_statements/pg_stat_statements.c | 4 ++-
3 files changed, 29 insertions(+), 27 deletions(-)