Create a separate HandlerThread to use for I/O operations

If we use main thread for I/O operations may have ANR issue.
Create a separate HandlerThread to avoid this.

Test: atest DocumentsUIGoogleTests:com.android.documentsui.archives.ReadableArchiveTest
Change-Id: I91748badfb1fd4ccda3f27a5c83a14591a4d9474
Fix: 129650074
1 file changed