Expand default optimizations

[justinchuby]

• Squeeze Reshape Identity optimization #2083

and others can be invoked by default

cc @titaiwangms

[gramalingam]

The various optimizations in llama rule set all look like good candidates to apply by default. Except for CastCast, which may require a minor fix to be sound [cast to type1 followed by cast to type2 should not be simplified, eg if type1 is lower precision than original type and type2].