Reland: Rewrite sbox to use a textproto manifest

This relands I3b918a6643cea77199fd39577ef71e34cdeacdb1 with a fix
to create the directory for the output depfile if doesn't exist.

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: I8af00c8c0b25a92f55a5032fcb525715ae8297c2