MooseMesh::buildLowerDMesh needs to add separate blocks for lower-d elements in different types

[YaqiWang]

Motivation

This is an issue often encountered in 3D meshes. Currently, the function adds two lower-d blocks, one for all interior sides and another for all boundary sides. In 3D, the sides could be in different element types, like either triangle, quad. This will cause an issue when writing the mesh into an Exodus mesh, where a mesh block must have the same element type.

Design

Even though calculations does not care lower-d element types, it could be a good idea to separate the mesh block into blocks based on the element types. We will need to add getters in MooseMesh to get a vector of interior side blocks and boundary side blocks, so that applications do not use Moose::INTERNAL_SIDE_LOWERD_ID or INTERNAL_SIDE_LOWERD_SUBDOMAIN directly. We need to add a test that contains elements like prism which have sides in different types.

Impact

Make calculations with lower-d mesh blocks able to perform Exodus outputs.