pgsql: Rethink blocking annotations in detach-partition-concurrently-[3

Rethink blocking annotations in detach-partition-concurrently-[34].

In 741d7f104, I tried to make the reports from canceled steps come out
after the pg_cancel_backend() steps, since that was the most common
ordering before. However, that doesn't ensure that a canceled step
doesn't report even later, as shown in a recent failure on buildfarm
member idiacanthus. Rather than complicating things even more with
additional annotations, let's just force the cancel's effect to be
reported first. It's not *that* unnatural-looking.

Back-patch to v14 where these test cases appeared.

Report: https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=idiacanthus&dt=2021-07-02%2001%3A40%3A04

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/9fa6fe466c9d2eaba4fdd8091203ee61e74d71bf

Modified Files
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.../expected/detach-partition-concurrently-3.out | 126 ++++++++++++---------
.../expected/detach-partition-concurrently-4.out | 56 +++++----
.../specs/detach-partition-concurrently-3.spec | 40 +++----
.../specs/detach-partition-concurrently-4.spec | 38 +++----
4 files changed, 143 insertions(+), 117 deletions(-)