convert all of Sage library code to libgap

[dimpase]

It's about time. The sooner this is done, the fewer code to cross pexpect gap/libgap boundary will have to be written. Some concrete tickets aiming at this:

#26750

Use GroupHomset_libgap for permutation groups, as well

#26889

use libGAP in MatrixGroup.as_permutation_group()

#27234

Implement method `gap` of class `PermutationGroupElement` properly.

#28504

conversion of posets to libgap

#28818

from gap to libgap in strongly_regular_db

#28820

convert guava interface to libgap

Also related:

#27878

Remove the "-r" option in calling gap in the pexpect interface

#27911

Do not restrict libgap.xxx to a predefined list

#27923

libgap: do not restrict libgap.<tab> completion to a fixed list

Following completion of this work, we can look into formally deprecating the pexpect interface to GAP: #26963.

[embray]

Retarging tickets optimistically to the next milestone. If you are responsible for this ticket (either its reporter or owner) and don't believe you are likely to complete this ticket before the next release (8.7) please retarget this ticket's milestone to sage-pending or sage-wishlist.

[soehms]

I've created a follow up ticket #27234 to #26750, since by the improvements in connection with GAP 4.10 upgrade, the implementation of the gap method of class PermutationGroupElement can be done properly, right now.

[embray]

Ticket retargeted after milestone closed (if you don't believe this ticket is appropriate for the Sage 8.8 release please retarget manually)

[embray]

As the Sage-8.8 release milestone is pending, we should delete the sage-8.8 milestone for tickets that are not actively being worked on or that still require significant work to move forward. If you feel that this ticket should be included in the next Sage release at the soonest please set its milestone to the next release milestone (sage-8.9).