We continue the cleaning of strongly_regular_db.pyx.

This ticket is built on top of #34311 and #34312 to avoid conflicts.

Depends on #34311
Depends on #34312

CC: @fchapoton @tscrim

Component: graph theory

Author: David Coudert

Branch/Commit: f2323c0

Reviewer: Kwankyu Lee

Issue created by migration from https://trac.sagemath.org/ticket/34313