Allow non-resizable apps in split-screen (5/n)

Replace usages of DEVELOPMENT_ENABLE_SIZECOMPAT_FREEFORM with
DEVELOPMENT_ENABLE_NON_RESIZABLE_MULTI_WINDOW so that we can use one
setting to control all multi window mode

Bug: 176061101
Test: pass existing
Change-Id: I873b4902f3995815721401b30236919ffdbc6a82