Deprecate targetSandboxVersion=2

Most of the targetSandboxVersion=2 protections have moved to target O
MR1 or P, or were reverted, so move the remaining checks to isInstantApp
and remove the requirement for Instant Apps to target
targetSandboxVersion=2

Change-Id: I448a7565e26d4eafece1bdc657192117d790ff3a
Fixes: 111314398
Test: atest cts/hostsidetests/appsecurity/src/android/appsecurity/cts/EphemeralTest.java