code/source: remove compiling functions

A lot of complex code that isn't used anymore outside of tests after
the previous commit.

src/_pytest/_code/__init__.py

@@ -7,7 +7,6 @@ from .code import getfslineno
 from .code import getrawcode
 from .code import Traceback
 from .code import TracebackEntry
-from .source import compile_ as compile
 from .source import Source
 
 __all__ = [
@@ -19,6 +18,5 @@ __all__ = [
     "getrawcode",
     "Traceback",
     "TracebackEntry",
-    "compile",
     "Source",
 ]