pgsql: Add recovery/startup test with backup_label and missing checkpoi

Add recovery/startup test with backup_label and missing checkpoint segment

This test is able to trigger the following failure at the beginning of
recovery, that was not covered yet:
FATAL: could not locate required checkpoint record at %X/%X

Note that the backup used for the node created has its pg_wal/ removed,
which is why the segment expected is missing.

Extracted from a larger patch by the same author.

Author: Nitin Jadhav <nitinjadhavpostgres(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAMm1aWZ9Tv=Wrx52_2Ppw+6ULf_twRZuQm=ZWLA_a-kXWykHkQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2b8598a2b045b172a8f726ba130e9eb764dc0688

Modified Files
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src/test/recovery/t/042_low_level_backup.pl | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)