pgsql: Fix CREATE INDEX CONCURRENTLY for simultaneous prepared transact

Fix CREATE INDEX CONCURRENTLY for simultaneous prepared transactions.

In a cluster having used CREATE INDEX CONCURRENTLY while having enabled
prepared transactions, queries that use the resulting index can silently
fail to find rows. Fix this for future CREATE INDEX CONCURRENTLY by
making it wait for prepared transactions like it waits for ordinary
transactions. This expands the VirtualTransactionId structure domain to
admit prepared transactions. It may be necessary to reindex to recover
from past occurrences. Back-patch to 9.5 (all supported versions).

Andrey Borodin, reviewed (in earlier versions) by Tom Lane and Michael
Paquier.

Discussion: https://postgr.es/m/2E712143-97F7-4890-B470-4A35142ABC82@yandex-team.ru

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/d1ab4bf6ed2d5d5026e13af510d0d3b025fa6ac9

Modified Files
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src/backend/storage/lmgr/lmgr.c | 3 +-
src/backend/storage/lmgr/lock.c | 43 +++++++++++++---------
src/include/storage/lock.h | 17 +++++----
src/test/isolation/Makefile | 11 +++---
src/test/isolation/README | 6 +--
.../expected/prepared-transactions-cic.out | 18 +++++++++
.../isolation/specs/prepared-transactions-cic.spec | 37 +++++++++++++++++++
7 files changed, 98 insertions(+), 37 deletions(-)