idmap2 code cleanup

- proper use of random number generators in FileUtils
- get rid of <iostream> include where possible
- replace std::endl with '\n' as we don't really need stream
  flushes
- added a few missed moves

Bug: 282215580
Test: build, UTs and boot
Change-Id: I2dbe5e7c240acd0f344158ae6d9f2ee2b9c2c6ab
diff --git a/cmds/idmap2/libidmap2/CommandLineOptions.cpp b/cmds/idmap2/libidmap2/CommandLineOptions.cpp
index 8129d99..888b3a5 100644
--- a/cmds/idmap2/libidmap2/CommandLineOptions.cpp
+++ b/cmds/idmap2/libidmap2/CommandLineOptions.cpp
@@ -19,8 +19,8 @@
 #include <algorithm>
 #include <cassert>
 #include <iomanip>
-#include <iostream>
 #include <memory>
+#include <ostream>
 #include <set>
 #include <sstream>
 #include <string>
@@ -131,7 +131,7 @@
       separator = true;
       stream << opt << ": missing mandatory option";
     }
-    stream << std::endl;
+    stream << '\n';
     Usage(stream);
     return Error("%s", stream.str().c_str());
   }
@@ -168,7 +168,7 @@
       out << " [" << opt.name << " arg [..]]";
     }
   }
-  out << std::endl << std::endl;
+  out << "\n\n";
   for (const Option& opt : options_) {
     out << std::left << std::setw(maxLength);
     if (opt.argument) {
@@ -181,7 +181,7 @@
         opt.count == Option::COUNT_OPTIONAL_ONCE_OR_MORE) {
       out << " (can be provided multiple times)";
     }
-    out << std::endl;
+    out << '\n';
   }
 }