Add strict flag in transaction

Add a flag named strict_ indicating whether we are compiling app images,
which need more strict constraints to control <clinit>s' behavours.

When the transaction is marked as strict mode, behaviour changes
including nested transactions, field access validation, memory
consumption limit and time out for <clinit> at compile time.

Test: make test-art-host -j64

Change-Id: I7cc0eea161803ad0d7763725d4deaeee21858054