gnucash stable: [trep-engine] improve readability of left-columns

[Christopher Lam]

Updated	 via  https://github.com/Gnucash/gnucash/commit/20970feb (commit)
	from  https://github.com/Gnucash/gnucash/commit/08e9f48f (commit)



commit 20970febed7fe99a1ba3f9c323ad2dd9a33a8dd9
Author: Christopher Lam <christopher.lck at gmail.com>
Date:   Sat Apr 29 12:25:41 2023 +0800

    [trep-engine] improve readability of left-columns
    
    similar to 93dd19e98b, change left-columns to use an assoc-list
    instead of a vector. left-columns is not a customisable object, so
    there's no need for a backward compatibility path.



Summary of changes:
 gnucash/report/trep-engine.scm | 223 +++++++++++++++++++++--------------------
 1 file changed, 115 insertions(+), 108 deletions(-)