Add apex info to the streaming property file

So updaters can streaming download the file, and query the apex info
inside the file.

Bug: 190244686
Test: generate an OTA package, check the streaming property
Change-Id: I17078d3f8d60ca53c6afe82f74b232e2fb242467

tools/releasetools/ota_from_target_files.py

@@ -530,6 +530,8 @@ class StreamingPropertyFiles(PropertyFiles):
         'payload_properties.txt',
     )
     self.optional = (
+        # apex_info.pb isn't directly used in the update flow
+        'apex_info.pb',
         # care_map is available only if dm-verity is enabled.
         'care_map.pb',
         'care_map.txt',