Resolve "Add support for nonlinear boundary conditions"

Closes #114

See merge request mechanics-and-materials/ae108!103

- solver ALMM not supported for complex scalar type

- includes tests with invalid definition and/or missing executable
- adds support for testing selection of executables

- based on Basic example
- check output of example in tests

- tests now pass when run with 3 MPI ranks

- supports nonlinear boundary conditions
- note: unit tests fail in MPI-parallel

- some solvers provided by TAO support these constraints

Resolve "Speed up CI using needs keyword"

Closes #117

See merge request mechanics-and-materials/ae108!106

- potentially speeds up CI due to more opportunity for parallelization

Resolve "Add JSON schema for test configuration files"

Closes #116

See merge request mechanics-and-materials/ae108!105

- ensures that configuration files of passing tests conform to schema
- validity of definition files is now checked in CI

- editors may provide suggestions based on the schema

- supports editing test definition files

Resolve "Add bar element (2D, 3D)"

Closes #115

See merge request mechanics-and-materials/ae108!104

- number of degrees of freedom differs between TimoshenkoBeamElement and Bar

Resolve "Simplify GTest find module"

Closes #113

See merge request mechanics-and-materials/ae108!102

- building library no longer required
- find module no longer required

Resolve "VTK fails to open XDMF for large topologies"

Closes #112

See merge request mechanics-and-materials/ae108!101

- vtk import of large datasets in xdmf/xml fails

Resolve "Segmentation faults for larger simulations"

Closes #111

See merge request mechanics-and-materials/ae108!100

Resolve "Simplify working with containers"

Closes #110

See merge request mechanics-and-materials/ae108!99

- allow running executables with mpirun as root by default
- workaround "Read -1" errors

Resolve "Update reference platform to Ubuntu Jammy"

Closes #98

See merge request mechanics-and-materials/ae108!87

- required on Euler cluster

Resolve "Add 'CantileverBeam' example"

Closes #85

See merge request mechanics-and-materials/ae108!74

- topological dimension no longer required
- add const

Resolve "Coverage badge does not show percentage"

Closes #109

See merge request mechanics-and-materials/ae108!98

Resolve "Memory leaks in `cpppetsc::Mesh`"

Closes #106

See merge request mechanics-and-materials/ae108!96

- fixes memory leaks