pgsql: Move VM update code from lazy_scan_heap() to lazy_scan_prune().

Move VM update code from lazy_scan_heap() to lazy_scan_prune().

Most of the output parameters of lazy_scan_prune() were being
used to update the VM in lazy_scan_heap(). Moving that code into
lazy_scan_prune() simplifies lazy_scan_heap() and requires less
communication between the two.

This change permits some further code simplification, but that
is left for a separate commit.

Melanie Plageman, reviewed by me.

Discussion: http://postgr.es/m/CAAKRu_aM=OL85AOr-80wBsCr=vLVzhnaavqkVPRkFBtD0zsuLQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/cb970240f13df2b63f0410f81f452179a2b78d6f

Modified Files
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src/backend/access/heap/vacuumlazy.c | 226 ++++++++++++++++++-----------------
1 file changed, 115 insertions(+), 111 deletions(-)