pgsql: Fix interference between cavering indexes and partitionedtables

Fix interference between cavering indexes and partitioned tables

The bug is caused due to the original IndexStmt that DefineIndex receives
being overwritten when processing the INCLUDE columns. Use separate list of
index params to propagate to child tables. Add tests covering this case.

Amit Langote and Alexander Korotkov.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5c6110c6a960ad6fe1b0d0fec6ae36ef4eb913f5

Modified Files
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src/backend/commands/indexcmds.c       | 27 ++++++++++++++-------------
src/test/regress/expected/indexing.out | 24 ++++++++++++++++++++++++
src/test/regress/sql/indexing.sql      | 19 +++++++++++++++++++
3 files changed, 57 insertions(+), 13 deletions(-)