Rewrite sbox to use a textproto manifest

In preparation for more complicated sandboxing that copies tools
and/or inputs into the sandbox directory, make sbox use a textproto
input that describes the commands to be run and the files to copy
in or out of the sandbox.

Bug: 124313442
Test: m checkbuild
Test: rule_builder_test.go
Test: genrule_test.go
Change-Id: I3b918a6643cea77199fd39577ef71e34cdeacdb1

android/Android.bp

@@ -4,6 +4,7 @@ bootstrap_go_package {
     deps: [
         "blueprint",
         "blueprint-bootstrap",
+        "sbox_proto",
         "soong",
         "soong-android-soongconfig",
         "soong-env",