[Android] Dinamically set test cases dir under app's specific storage

[IvanBM18]

Bug: b/545195031

Since Android API level 30(and all apps targeting android 11+), apps have scoped storage access, and we can only give it external storage permissions at runtime by a user facing dialog. To avoid this, we now copy the testcases to the app's external app-specific storage , which is always readable by our app's package.

We didn't noticed this issues because all test cases execute using am start which almost the 99% of the time returns no error codes, hence we though that the test case executed but that is not the case.

Example for chrome: Previously, if we tried to execute our test case, the app would tell us it can't find the file(because of the read external storage permissions):
TODO
But after this changes the html renders successfully!
TODO

Learn more:

• https://developer.android.com/about/versions/11/privacy/storage
• https://developer.android.com/training/data-storage#scoped-storage

Alternative

• The other alternative is to serve the testcases html/js/css files trough a simple localhost server trough adb reverse tcp:8000 tcp:8000, this is what we usually do in regular chrome tests, clusterfuzz already support's this, but i think nevertheless we need to make this change to keep our options open.

Changes

• Always pushes files to this directory /sdcard/Android/data/{PKG_NAME}/files/ which is always reable by the given app.
• Dynamically calculate the Test case directory based off the app's pkg
• Now at fuzz session setup we clean from /sdcard/Android/data/{PKG_NAME}/files/*.

Tests performed

[IvanBM18]

Maybe i should always grab the default value here, this way jobs that already define a custom test cases dir path continue to work