Embms adjustments for 7/28

* Move some vendor intents and extras into a VendorIntents class
* Add a download result RESULT_IO_ERROR
* Add documentation noting that repeated calls to
setTempFileRootDirectory will not throw an error if the parameter is the
same.
* Add getTempFileRootDirectory method for app
* Hide AIDL classes from the public/system API surfaces for download
* Remove size and md5hash from FileInfo

Test: testapps
Bug: 30981736
Change-Id: I8c968a7d68db2588ee550167ed2693fe89c5925a