Adjust packages to avoid unnecessary uses of `IsContainedInSpan`

[fingolfin]

A bunch of packages could potentially benefit from similar changes. Her are all that use IsContainedInSpan:

$ rg --type=gap -l IsContainedInSpan pkg/   | sort | cut -d/ -f2 | uniq
corelg
ctbllib
fining
liealgdb
polycyclic
qpa
recog
repsn
sla

Originally posted by @fingolfin in #6287 (comment)