refactor!: tests and fixtures

[TechyDaniel]

• Add Mesh protocol, so any mesh class potentially returned by a reader must implement the protocol.
• Add tests for reading meshes from file.
• Add pytest fixtures to use re-use mocked data across tests.
• Refactor get_border_vertices to get_boundary_vertices that taked an array instead of a mesh instance, so it's less greedy.

Description

We now accept edges as input into the get_boundary_vertices.
Those vertices are extracted in a different function which is designed to work regardless of the mesh data structure input.

Task: TECHART-323

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• locally
• github action

Test Configuration:

• hatch commands

Checklist

• I confirm that the changes meet the user experience and goals outlined in the design plan (if there is one).
• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have updated any version info, if necessary.
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[Olaf-Wolf3D]

let's butcher this PR for a learning experience! :D