Override flag in PipController/PipTaskOrg.Test

PipController and PipTaskOrganizer in pip1 package
check for whether PiP2 flag is off before registering
certain listeners. These calls are actually checked
through verify() assertions in their respective unit tests.

So we should override the PiP2 flag to be disabled for these
unit tests (they still run but with enable_pip2=false always).

Also added myself to the list OWNERS in the wm.shell tests package.

Bug: 375599908
Flag: com.android.wm.shell.enable_pip2
Test: atest WMShellUnitTests
Change-Id: Iba57605d83c4e182dd30f06a34f534b70a938c2c