[CDAP-19529] Move SparkTwillRunnable to cdap-app-fabric

[dli357]

Context: keeping it in the spark extension module can cause an environment to fail when it has not yet loaded runtime extensions. Considering SparkTwillRunnable has no dependency on spark itself, it should be ok to move it to cdap-app-fabric; in fact, it should be there as a first-class citizen because it fits into the current paradigm of CDAP being aware of the program type (ProgramType.SPARK) yet delegating the running of that program type to specific runtime extensions.

[gitpod-io[bot]]

[dli357]

Closing this PR in favor of #14536.