Fix Environment.isExternalStorageLegacy() impl.

Earlier, this API only used to consider op_legacy_storage
appop to decide whether an app will get legacy storage view
or not but there are few other factors it needs to consider
like whether the app has WRITE_MEDIA_STORAGE permission or
whether app was allowed to be an installer in which case it
will get legacy access.

Bug: 132760141
Test: atest cts/hostsidetests/appsecurity/src/android/appsecurity/cts/ExternalStorageHostTest.java
Change-Id: I227a171bf40e43e135e1a6dbc819cfad21d91520