Accept DexMetadata files (.dm) for install-multiple

Allow .dm files (DexMetadata) to be passed to adb install-multiple.

Do not rename the input files based on their indices as the naming matters
for associating an .dm file to an .apk file.

Test: adb install-multiple -p com.android.cts.classloadersplitapp base.apk
     split.apk split.dm

Bug: 30934496
Change-Id: I2ac39e00d64eae938124250033f79e02f3c3f9c0