Merge branch 'backport/bugfix-2p-analytic-derivatives' into 'releases/3.1'

Backport/bugfix 2p analytic derivatives

See merge request !1955 (merged)

(cherry picked from commit ebd8a468)

8557fb13 [2p][bugfix] Fix analytic storage derivatives d9662997 [2p] Correct signs of local variables for analytic flux derivative 73e385b2 [2p][bugfix] Fix equation index for analytic box Jacobian 961bda2b [2p] Fix sign of local derivative variables in box analytic Jacobian