Resolve "Create Release Issue template"

Closes #1008

See merge request !2641

[embedded] Make source stencil lookup slightly more efficient

See merge request !2653

[install] update script versions to 3.4

See merge request !2647

[couplingmapper] Improve locality of variable scope

See merge request !2650

[facet][boxmapper] avoid uninitialized warning variable

See merge request !2649

[cleanup][boxdfm] Remove CubeTopology deprecation warning

See merge request !2645

[mailmap][license] Update Theresas lastname in mailmap and license

See merge request !2642

[ci] test master branch in lecture

See merge request !2639

feature/refactor-test-selection

See merge request !2626

This can help interpreting the ci logic once we add pipelines for more 
events.

The idea is to evaluate differences between the current branch and the 
target branch for merge requests. Having a default we don't notice if 
this breaks when someone removes the target branch variable passed from 
the parent pipeline.

since we now run the test selection stage in the same container as the
build state, this is no longer necessary

also, do not only check the current project headers, as downstream
modules may want to test against changes in dumux

[md][box] Internal Dirichlet

See merge request !2637

* Set off-diagonal matrix blocks to zero if internal Dirichlet is set
* use correct problem() function in md framework

Use dumux_add_test

See merge request !2633

dumux_add_test makes additional checks and writes important files for the CI to work

[solver] Fix restartGMRes parameter number type

See merge request !2631

Revert "Merge branch 'fix/debug_sequential_2p_models_for_bcleverett_and_mcwhorter' into 'master'"

See merge request !2627

This reverts merge request !2608

Improve angeli test

See merge request !2607