init: support setting rlimits per service

Add a new service option, `rlimit` that allows a given rlimit to be
set for a specific service instead of globally.

Use the same parsing, now allowing text such as 'cpu' or 'rtprio'
instead of relying on the enum value for the `setrlimit` builtin
command as well.

Bug: 63882119
Bug: 64894637

Test: boot bullhead, run a test app that attempts to set its rtprio to
      95, see that the priority set fails normally but passes when
      `rlimit rtprio 99 99` is used as its service option.
      See that this fails when `rlimit rtprio 50 50` is used as well.
Test: new unit tests

Change-Id: I4a13ca20e8529937d8b4bc11718ffaaf77523a52
diff --git a/init/service.h b/init/service.h
index 1f2c44f..67542ca 100644
--- a/init/service.h
+++ b/init/service.h
@@ -17,6 +17,7 @@
 #ifndef _INIT_SERVICE_H
 #define _INIT_SERVICE_H
 
+#include <sys/resource.h>
 #include <sys/types.h>
 
 #include <memory>
@@ -138,6 +139,7 @@
     Result<Success> ParseMemcgSoftLimitInBytes(const std::vector<std::string>& args);
     Result<Success> ParseMemcgSwappiness(const std::vector<std::string>& args);
     Result<Success> ParseNamespace(const std::vector<std::string>& args);
+    Result<Success> ParseProcessRlimit(const std::vector<std::string>& args);
     Result<Success> ParseSeclabel(const std::vector<std::string>& args);
     Result<Success> ParseSetenv(const std::vector<std::string>& args);
     Result<Success> ParseShutdown(const std::vector<std::string>& args);
@@ -195,6 +197,8 @@
 
     unsigned long start_order_;
 
+    std::vector<std::pair<int, rlimit>> rlimits_;
+
     std::vector<std::string> args_;
 };