pgsql: Have pg_rewind run crash recovery before rewinding

Have pg_rewind run crash recovery before rewinding

If we don't do this, the rewind fails if the server wasn't cleanly shut
down, which seems unhelpful serving no purpose.

Also provide a new option --no-ensure-shutdown to suppress this
behavior, for alleged advanced usage that prefers to avoid the crash
recovery.

Authors: Paul Guo, Jimmy Yih, Ashwin Agrawal
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/CAEET0ZEffUkXc48pg2iqARQgGRYDiiVxDu+yYek_bTwJF+q=Uw@mail.gmail.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/5adafaf176d09ba5ea11ae128416fc5211469bc0

Modified Files
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doc/src/sgml/ref/pg_rewind.sgml | 15 ++++++++
src/bin/pg_rewind/pg_rewind.c   | 80 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 95 insertions(+)