Rename APEX file_contexts as <name>-file_context

It was <name>_file_context before. Changing for better readability.

Bug: 119034475
Test: m apex.test com.android.tzdata com.android.runtime
Change-Id: Ic9d6479dfed56ac474c574343a38b5f73dde3c05
diff --git a/apex/apex.test_file_contexts b/apex/apex.test-file_contexts
similarity index 100%
rename from apex/apex.test_file_contexts
rename to apex/apex.test-file_contexts
diff --git a/apex/com.android.media_file_contexts b/apex/com.android.media-file_contexts
similarity index 100%
rename from apex/com.android.media_file_contexts
rename to apex/com.android.media-file_contexts
diff --git a/apex/com.android.runtime_file_contexts b/apex/com.android.runtime-file_contexts
similarity index 100%
rename from apex/com.android.runtime_file_contexts
rename to apex/com.android.runtime-file_contexts
diff --git a/apex/com.android.tzdata_file_contexts b/apex/com.android.tzdata-file_contexts
similarity index 100%
rename from apex/com.android.tzdata_file_contexts
rename to apex/com.android.tzdata-file_contexts