Add a simple MappedFile to libbase and switch fastboot and libziparchive over.

This allows us to remove libziparchive's dependency on libutils.

Bug: http://b/79112958
Test: ran libbase and libziparchive tests, ran fastboot manually
Change-Id: I95c651976dad222863e5b8c37d4514b778f5dce7
diff --git a/base/Android.bp b/base/Android.bp
index daa820a..741664b 100644
--- a/base/Android.bp
+++ b/base/Android.bp
@@ -47,6 +47,7 @@
         "chrono_utils.cpp",
         "file.cpp",
         "logging.cpp",
+        "mapped_file.cpp",
         "parsenetaddress.cpp",
         "properties.cpp",
         "quick_exit.cpp",
@@ -124,6 +125,7 @@
         "file_test.cpp",
         "logging_test.cpp",
         "macros_test.cpp",
+        "mapped_file_test.cpp",
         "parsedouble_test.cpp",
         "parseint_test.cpp",
         "parsenetaddress_test.cpp",