pgsql: revert: add transaction processing chapter with internals info

revert:  add transaction processing chapter with internals info

This doc patch (master hash 66bc9d2d3e) was decided to be too
significant for backpatching, so reverted in all but master.  Also fix
SGML file header comment in master.

Reported-by:    Peter Eisentraut

Discussion: https://postgr.es/m/c6304b19-6ff7-f3af-0148-cf7aa7e2fbfd@enterprisedb.com

Backpatch-through: 11

Branch
------
REL_11_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/01e248f7966c0678645a5189bd2405218a7a5929

Modified Files
--------------
doc/src/sgml/catalogs.sgml              |   7 +-
doc/src/sgml/config.sgml                |   6 +-
doc/src/sgml/filelist.sgml              |   1 -
doc/src/sgml/monitoring.sgml            |   3 +-
doc/src/sgml/pgrowlocks.sgml            |   3 +-
doc/src/sgml/postgres.sgml              |   1 -
doc/src/sgml/ref/release_savepoint.sgml |  62 ++++------
doc/src/sgml/ref/rollback_to.sgml       |   5 +-
doc/src/sgml/wal.sgml                   |   6 +-
doc/src/sgml/xact.sgml                  | 200 --------------------------------
10 files changed, 32 insertions(+), 262 deletions(-)