pgsql: Split TuplesortPublic from Tuplesortstate

Split TuplesortPublic from Tuplesortstate

The new TuplesortPublic data structure contains the definition of
sort-variant-specific interface methods and the part of Tuple sort operation
state required by their implementations.  This will let define Tuple sort
variants without knowledge of Tuplesortstate, that is without knowledge
of generic sort implementation guts.

Discussion: https://postgr.es/m/CAPpHfdvjix0Ahx-H3Jp1M2R%2B_74P-zKnGGygx4OWr%3DbUQ8BNdw%40mail.gmail.com
Author: Alexander Korotkov
Reviewed-by: Pavel Borisov, Maxim Orlov, Matthias van de Meent
Reviewed-by: Andres Freund, John Naylor

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ec92fe98356a8a36427fe9ef52873b50fe17852e

Modified Files
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src/backend/utils/sort/tuplesort.c | 814 +++++++++++++++++++++----------------
src/tools/pgindent/typedefs.list   |   6 +
2 files changed, 471 insertions(+), 349 deletions(-)