pgsql: doc: Fix descriptions of some PGC_POSTMASTER parameters.

doc: Fix descriptions of some PGC_POSTMASTER parameters.

The following parameters can only be set at server start because
their context is PGC_POSTMASTER, but this information was missing
or incorrectly documented. This commit adds or corrects
that information for the following parameters:

* debug_io_direct
* dynamic_shared_memory_type
* event_source
* huge_pages
* io_max_combine_limit
* max_notify_queue_pages
* shared_memory_type
* track_commit_timestamp
* wal_decode_buffer_size

Backpatched to all supported branches.

Author: Karina Litskevich <litskevichkarina@gmail.com>
Reviewed-by: Chao Li <lic@highgo.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CAHGQGwGfPzcin-_6XwPgVbWTOUFVZgHF5g9ROrwLUdCTfjy=0A@mail.gmail.com
Backpatch-through: 13

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/a2e17a2bb20018c0e46a9538e547542cae030103

Modified Files
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doc/src/sgml/config.sgml | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)