0.5.2: Change update all `third_party` dependencies

[adamkewley]

Related: #634

Stub issue for doing that.

• [x] benchmark (fc3fd6a)
• [x] glew (not necessary - hasn't changed)
• [x] glm
• [x] googletest
• [x] lunasvg
• [x] nativefiledialog (not necessary - hasn't changed)
• [x] SDL
• [x] span-lite (not necessary - hasn't changed)
• [x] stb (not necessary - hasn't changed)
• [x] tomlplusplus (not necessary - no new releases)
• [x] unordered_dense
• [x] imgui
• [x] ImGuizmo
• [x] implot
• [x] opensim-core
  • [x] And check CHANGELOG for any changes that may impact opensim-creator
  • [x] And check TODOs in opensim-creator for any potential new bugfixes that can now be deleted
  • [x] And check the test suite for "known bugs" that are now fixed
  • [x] And check the test suite for DISABLED stuff that may now be enable-able