Issue with PeripheralTriangleMeshGenerator-defined external sideset and block naming

[sallustius]

Bug Description

If the PeripheralTriangleMeshGenerator is used more than once in the same mesh, it does not generate the correct external sideset and does not save the block names assigned in previous instruction block. It may be a problem with XYDelaunayGenerator, as @miaoyinb pointed out. An example of consecutive use is reported below and in the attached input file:

     [tmg1]
      type = PeripheralTriangleMeshGenerator
      input = pattern
      peripheral_ring_radius = ${r1}
      peripheral_ring_block_id = 250
      peripheral_ring_num_segments = 50
      peripheral_ring_block_name = peripheral_1
      desired_area = .2
    []
    [pr2]
      type = PeripheralTriangleMeshGenerator
      input = tmg1
      peripheral_ring_radius = ${r2}
      peripheral_ring_num_segments = 80
      peripheral_ring_block_id = 150
      peripheral_ring_block_name = peripheral_2
      desired_area = 1
      external_boundary_name = 'external' # Does not work
    []

Steps to Reproduce

Run the attached input file with mesh-only option. If you inspect the output, you will see that the "external" sideset is not the external one.

issue_trianglemeshgenerator.txt

Impact

Users won't be able to generate the correct sideset or block assignment if PeripheralTriangleMeshGenerator is used more than once. Mitigation: You can use ParsedSideSetGenerator and RenameBlockGenerator to ensure block names and sidesets are assigned/defined correctly.