Introduce apex_info_file type

/apex/apex-info-file.xml is labeled as apex_info_file. It is
created/written by apexd once by apexd, and can be read by zygote and
system_server. The content of the file is essentially the same as the
return value of getAllPackages() call to apexd.

Bug: 154823184
Test: m
Merged-In: Ic6af79ddebf465b389d9dcb5fd569d3a786423b2
(cherry picked from commit f1de4c02cc3da98d052ca81e48e7d4682eea6088)
Change-Id: Ic6af79ddebf465b389d9dcb5fd569d3a786423b2
8 files changed