pgsql: Make vacuum a bit more verbose to debug BF failure.

Make vacuum a bit more verbose to debug BF failure.

This is temporary. While possibly some more error checking / debugging
in this path would be a good thing, it'll not look exactly like this.

Discussion: https://postgr.es/m/20200816181604.l54m6kss5ntd6xow@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/49967da65aec970fcda123acc681f1df5d70bfc6

Modified Files
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src/backend/access/heap/heapam.c     | 11 ++++++++++-
src/backend/access/heap/vacuumlazy.c |  7 +++++++
2 files changed, 17 insertions(+), 1 deletion(-)