bloaty: measure stripped Rust binaries

Modify bloaty's MeasureSizeForPath to allow a module to provide multiple
paths. This is used to measure both unstripped and stripped
libraries/binaries. Add unit test to ensure correct measurements are
generated for Rust.

Test: m out/soong/binary_sizes.pb.gz
Change-Id: I59439b77dbf1cf5ad71e1c02996a6a90938536b4

bloaty/Android.bp

@@ -11,6 +11,7 @@ bootstrap_go_package {
     ],
     srcs: [
         "bloaty.go",
+        "testing.go",
     ],
     pluginFor: ["soong_build"],
 }