Support installation of DexMetadata files (.dm)

Add support in the package installer to install dex metadata files
alongside the application apks (base or splits).

During installation or update the dex metadata files will need to have a
matching apk file. The matching is done by checking the file extension
(e.g. base.apk -> base.dm, split_a.apk -> split.dm).

On disk, the metadata files are placed next to the apks.

The .dm files will be used during install-time optimizations and passed
verbatim to dex2oat.

Test: adb shell am instrument -w \
1) adb shell am instrument -w \
  -e class android.content.pm.DexMetadataHelperTest

com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner

2) adb install-multiple CtsClassloaderSplitApp.apk
CtsClassloaderSplitApp.dm CtsClassloaderSplitAppFeatureA.apk
CtsClassloaderSplitAppFeatureA.dm CtsClassloaderSplitAppFeatureB.apk

3) gts-tradefed -m GtsAndroidRuntimeManagerHostTestCases

Bug: 30934496

Change-Id: I86f0a8307705ff3d6a5a85c2fcaae085dd62d4af