pgsql: Use streaming read I/O in autoprewarm

Use streaming read I/O in autoprewarm

Make a read stream for each valid fork of each valid relation
represented in the autoprewarm dump file and prewarm those blocks
through the read stream API instead of by directly invoking
ReadBuffer().

Co-authored-by: Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com>
Co-authored-by: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Reviewed-by: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Reviewed-by: Andrey M. Borodin <x4mmm(at)yandex-team(dot)ru> (earlier versions)
Reviewed-by: Kirill Reshke <reshkekirill(at)gmail(dot)com> (earlier versions)
Reviewed-by: Matheus Alcantara <mths(dot)dev(at)pm(dot)me> (earlier versions)
Discussion: https://postgr.es/m/flat/CAN55FZ3n8Gd%2BhajbL%3D5UkGzu_aHGRqnn%2BxktXq2fuds%3D1AOR6Q%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d9c7911e1a5f354b7c34b7f53a52e0a690e7ebc9

Modified Files
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contrib/pg_prewarm/autoprewarm.c | 126 ++++++++++++++++++++++++++++++++-------
src/tools/pgindent/typedefs.list | 1 +
2 files changed, 104 insertions(+), 23 deletions(-)