pgsql: Add helper functions to simplify heapgettup code

Add helper functions to simplify heapgettup code

Here we add heapgettup_start_page() and heapgettup_continue_page() to
simplify the code in the heapgettup() function.

Author: Melanie Plageman
Reviewed-by: David Rowley
Discussion: https://postgr.es/m/CAAKRu_bvkhka0CZQun28KTqhuUh5ZqY=_T8QEqZqOL02rpi2bw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/8ca6d49f634124e2f77f5c02af244c4ca4a3b1e9

Modified Files
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src/backend/access/heap/heapam.c | 118 +++++++++++++++++++++++++++------------
1 file changed, 83 insertions(+), 35 deletions(-)