add region class and tests

[KatKatKateryna]

Description & motivation

Replicate C# Region class: specklesystems/speckle-sharp-sdk#241

"New Region class is a flat geometry represented by the boundary curve and inner loop curves, which hostApp turns into a planar filled geometry (or, Region). Hatch ("region" with a pattern or gradient fill) is a type of new Region class with a property "hasHatchPattern=true".

Currently the displayValue is a list of Meshes (for the apps that can triangulate meshes). We hope that in the future the Viewer can support this geometry and create a fill in the Viewer, without the need to generate and send an extra Mesh."

Changes:

To-do before merge:

Screenshots:

Validation of changes:

Checklist:

• My pull request follows the guidelines in the Contributing guide?
• My pull request does not duplicate any other open Pull Requests for the same update/change?
• My commits are related to the pull request and do not amend unrelated code or documentation.
• My code follows a similar style to existing code.
• I have added appropriate tests.
• I have updated or added relevant documentation.

References