pgsql: Doc: subdivide System Information Functions and Operators.

Doc: subdivide System Information Functions and Operators.

Provide <sect2> subdivisions in 9.26 System Information Functions and
Operators.  This is useful because it adds a mini-TOC at the top of
the page to aid jumping to portions of what's become quite a long
section.  Also, now that several of the subsections contain multiple
tables, it's hard to see the overall structure without headings.

Discussion: https://postgr.es/m/4026789.1670426602@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3b3182195304777430d16d7967f0adcd8dbfe2ed

Modified Files
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doc/src/sgml/func.sgml | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 50 insertions(+)