pgsql: Replace lateral references to removed rels in subqueries

Replace lateral references to removed rels in subqueries

This commit introduces a new field 'sublevels_up' in ReplaceVarnoContext,
and enhances replace_varno_walker() to:
1) recurse into subselects with sublevels_up increased, and
2) perform the replacement only when varlevelsup is equal to sublevels_up.

This commit also fixes some outdated comments. And besides adding relevant
test cases, it makes some unification over existing SJE test cases.

Discussion: https://postgr.es/m/CAMbWs4-%3DPO6Mm9gNnySbx0VHyXjgnnYYwbN9dth%3DTLQweZ-M%2Bg%40mail.gmail.com
Author: Richard Guo
Reviewed-by: Andrei Lepikhov, Alexander Korotkov

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/466979ef031afff000f3f92b812b946cf3a416c1

Modified Files
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src/backend/optimizer/plan/analyzejoins.c | 147 ++++++++--------
src/test/regress/expected/join.out | 278 +++++++++++++++---------------
src/test/regress/sql/join.sql | 218 ++++++++++++-----------
3 files changed, 337 insertions(+), 306 deletions(-)