otautil: Factor out the utils that're private to recovery.

A number of utility functions are intended for serving recovery's own
use. Exposing them via libotautil (which is a static lib) would pass the
dependencies onto libotautil's users (e.g. recovery image, updater, host
simulator, device-specific recovery UI/updater extensions etc). This CL
finds a new home for the utils that are private to recovery.

Test: mmma bootable/recovery
Change-Id: I575e97ad099b85fe1c1c8c7c9458a5a43d4e11e1

tests/unit/parse_install_logs_test.cpp

@@ -22,7 +22,7 @@
 #include <android-base/strings.h>
 #include <gtest/gtest.h>
 
-#include "otautil/parse_install_logs.h"
+#include "recovery_utils/parse_install_logs.h"
 
 TEST(ParseInstallLogsTest, EmptyFile) {
   TemporaryFile last_install;