WIP: ENH: Bump elastix version to 2023-04-30

Including:

  pull request SuperElastix/elastix#864
  commit SuperElastix/elastix@c3d478e
  "ENH: Upgrade elastix from C++14 to C++17"

  pull request SuperElastix/elastix#856
  commit SuperElastix/elastix@48c6458
  "ENH: Add SetInitialTransformParameterObject to ElastixRegistrationMethod"

  pull request SuperElastix/elastix#832
  commit SuperElastix/elastix@05d2b40
  ENH: Support "ShowProgressPercentage" parameter (`false` by default)

  pull request SuperElastix/elastix#815
  commit SuperElastix/elastix@c4ef707
  "ENH: Add `ElastixLogLevel` to the ITK interface"

  pull request SuperElastix/elastix#799
  "Replace our xout library with Gabi Melman's spdlog"
  commit SuperElastix/elastix@085a393
  "ENH: Add spdlog (v1.11.0) to ThirdParty subdirectory as git submodule"

CMakeLists.txt

@@ -51,7 +51,7 @@ if(SKBUILD)
 endif()
 
 set(elastix_GIT_REPOSITORY "https://github.com/SuperElastix/elastix.git")
-set(elastix_GIT_TAG "d652938573e5f193955908eba225a854b31ce36a")
+set(elastix_GIT_TAG "ec8034ddebf465da65dcedef4db2c2bf6f982f9c")
 FetchContent_Declare(
   elx
   GIT_REPOSITORY ${elastix_GIT_REPOSITORY}