Add in-source build script for examples/tutorials

[jslee02]

This PR is prerequisite work for having examples and tutorials with various build settings like requiring additional dependencies. Up to now, in-source building for examples and tutorials was handled by macros (i.e., dart_add_example and dart_add_tutorial), but it wouldn't be straightforward to handle various build settings.

This PR adds separate build scripts for in-source builds (based on this suggestion). We are still able to build examples/tutorials out of source with installed DART.

Caveat

• I found that osgWamIkFast doesn't work (at least on Ubuntu), and this will be addressed in another PR.
• Out-of-source builds are not tested.

---

Before merging a pull request

• Set version target by selecting a milestone on the right side
• Once Update vcpkg before installing packages #1018 is merged into release-6.4, merge release-6.4 into this PR

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.4@93215cf). Click here to learn what that means.
The diff coverage is n/a.

@@              Coverage Diff               @@
##             release-6.4    #1015   +/-   ##
==============================================
  Coverage               ?   56.58%           
==============================================
  Files                  ?      314           
  Lines                  ?    24312           
  Branches               ?        0           
==============================================
  Hits                   ?    13758           
  Misses                 ?    10554           
  Partials               ?        0