pgsql: Remove BufFile's isTemp flag.

Remove BufFile's isTemp flag.

The isTemp flag controls whether buffile.c chops BufFile data up into
1GB segments on disk.  Since it was badly named and always true, get
rid of it.

Author: Thomas Munro (based on suggestion by Peter Geoghegan)
Reviewed-By: Peter Geoghegan, Andres Freund
Discussion: https://postgr.es/m/CAH2-Wz%3D%2B9Rfqh5UdvdW9rGezdhrMGGH-JL1X9FXXVZdeeGeOJA%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/11e264517dff7a911d9e6494de86049cab42cde3

Modified Files
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src/backend/storage/file/buffile.c | 43 ++++++++++++++++----------------------
1 file changed, 18 insertions(+), 25 deletions(-)