pgsql: Provide a log_level setting for auto_explain

Provide a log_level setting for auto_explain

Up to now the log level has been hardcoded at LOG. A new
auto_explain.log_level setting allows that to be modified.

Discussion: https://postgr.es/m/CAPPfruyZh+snR2AdmutrA0B_caj=yWZkLqxUTZYNjJCaQ_wKQg@mail.gmail.com

Tom Dunstan and Andrew Dunstan
Reviewed by Daniel Gustafsson

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2d36a5e9dab6eda817b3d72a2d0f42c3d0cd922c

Modified Files
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contrib/auto_explain/auto_explain.c | 29 ++++++++++++++++++++++++++++-
doc/src/sgml/auto-explain.sgml      | 21 +++++++++++++++++++++
2 files changed, 49 insertions(+), 1 deletion(-)