Swift SIL: add the SmallProjectionPath utility

The `SmallProjectionPath` represents a path of value or address projections.
It’s used for defining argument effects for functions and for the new escape analysis.

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/RunUnitTests.swift

@@ -18,4 +18,7 @@ let runUnitTests = FunctionPass(name: "run-unit-tests", {
   (function: Function, context: PassContext) in
 
   print("--- Run unit tests ---")
+  
+  print("test ProjectionPath")
+  SmallProjectionPath.runUnitTests()
 })

SwiftCompilerSources/Sources/SIL/CMakeLists.txt

@@ -17,6 +17,7 @@ add_swift_compiler_module(SIL
   Location.swift
   Operand.swift
   Registration.swift
+  SmallProjectionPath.swift
   SubstitutionMap.swift
   Type.swift
   Utils.swift