Build merged apexkeys.txt/apkcerts.txt by partition.

Propagate partition tag data to apexkeys.txt and
apkcerts.txt so that merge_target_files.py can build
merged versions of these files by filtering the
framework files for framework partitions and filtering
the vendor files for vendor partitions.

Bug: 138942268
Change-Id: Ic3226728e97dae84d38ec230ccc86d1b124bea94

tools/releasetools/common.py

@@ -1754,7 +1754,8 @@ def ReadApkCerts(tf_zip):
       continue
     m = re.match(
         r'^name="(?P<NAME>.*)"\s+certificate="(?P<CERT>.*)"\s+'
-        r'private_key="(?P<PRIVKEY>.*?)"(\s+compressed="(?P<COMPRESSED>.*)")?$',
+        r'private_key="(?P<PRIVKEY>.*?)"(\s+compressed="(?P<COMPRESSED>.*)")?'
+        r'(\s+partition="(?P<PARTITION>.*)")?$',
         line)
     if not m:
       continue