pgsql: Make use FullTransactionId in 2PC filenames

Make use FullTransactionId in 2PC filenames

Switch from using TransactionId to FullTransactionId in naming of 2PC files.
Transaction state file in the pg_twophase directory now have extra 8 bytes in
the name to address an epoch of a given xid.

Author: Maxim Orlov, Aleksander Alekseev, Alexander Korotkov, Teodor Sigaev
Author: Nikita Glukhov, Pavel Borisov, Yura Sokolov
Reviewed-by: Jacob Champion, Heikki Linnakangas, Alexander Korotkov
Reviewed-by: Japin Li, Pavel Borisov, Tom Lane, Peter Eisentraut, Andres Freund
Reviewed-by: Andrey Borodin, Dilip Kumar, Aleksander Alekseev
Discussion: https://postgr.es/m/CACG%3DezZe1NQSCnfHOr78AtAZxJZeCvxrts0ygrxYwe%3DpyyjVWA%40mail.gmail.com
Discussion: https://postgr.es/m/CAJ7c6TPDOYBYrnCAeyndkBktO0WG2xSdYduTF0nxq%2BvfkmTF5Q%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5a1dfde8334b25e19bf4b3aa75274c547a3aa30f

Modified Files
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src/backend/access/transam/twophase.c | 50 +++++++++++++++++++++++++++++++----
1 file changed, 45 insertions(+), 5 deletions(-)