Refactoring Targets

Prioritize improvements to these files since they have the highest technical debt interest rate.


coreclr/src/jit/morph.cpp
coreclr/src/jit/importer.cpp
coreclr/src/jit/gentree.cpp
coreclr/src/jit/lower.cpp
coreclr/src/jit/codegenxarch.cpp
coreclr/src/jit/flowgraph.cpp
coreclr/src/jit/lsra.cpp
coreclr/src/jit/compiler.cpp
coreclr/src/jit/codegencommon.cpp
coreclr/src/vm/jitinterface.cpp
coreclr/src/gc/gc.cpp
coreclr/src/jit/codegenlegacy.cpp