Added job structure persistence to job_list update_geneaology().
When job_list generation is called and transitive reduction is executed, Autosubmit will try to save the resulting dependency structure to reuse it in following calls and avoid doing transitive reduction repeatedly.
The persistence database is saved in /esarchive/autosubmit/expid/pkl/ as structure_expid.db.
If the method detects that the experiment structure has changed, it will recreate the table that stores the structure.
Currently, this method is automatic and does not require any flag from the user. After testing, the overhead it adds the first time it creates the persistence file is non-noticeable but the benefit is remarkable, so I decided to include it as automatic. Also, verification is rigorous.